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Hay

Hay is grass, legumes, or other herbaceous plants that have been cut and dried to be stored for use as animal fodder, either for large grazing animals raised as livestock, such as cattle, horses, goats, and sheep, or for smaller domesticated animals such as rabbits and guinea pigs. Pigs can eat hay, but do not digest it as efficiently as herbivores do.

Hay can be used as animal fodder when or where there is not enough pasture or rangeland on which to graze an animal, when grazing is not feasible due to weather (such as during the winter), or when lush pasture by itself would be too rich for the health of the animal. It is also fed when an animal cannot access any pastures—for example, when the animal is being kept in a stable or barn.

Hay production and harvest, commonly known as "making hay", "haymaking", "haying" or "doing hay", involves a multiple step process: cutting, drying or "curing", raking, processing, and storing. Hayfields do not have to be reseeded each year in the way that grain crops are, but regular fertilizing is usually desirable, and overseeding a field every few years helps increase yield.

Composition

Commonly used plants for hay include mixtures of grasses such as ryegrass (Lolium species), timothy, brome, fescue, Bermuda grass, orchard grass, and other species, depending on region. Hay may also include legumes, such as alfalfa (lucerne) and clovers (red, white and subterranean). Legumes in hay are ideally cut pre-bloom. Other pasture forbs are also sometimes a part of the mix, though these plants are not necessarily desired as certain forbs are toxic to some animals.

In the UK some hay is harvested from traditionally managed hay meadows which have a highly diverse flora and which support a rich eco-system. The hay produced by these meadows is species rich and was traditionally used to feed horses.

Oat, barley, and wheat plant materials are occasionally cut green and made into hay for animal fodder, and more usually used in the form of straw, a harvest byproduct of stems and dead leaves that are baled after the grain has been harvested and threshed. Straw is used mainly for animal bedding. Although straw is also used as fodder, particularly as a source of dietary fiber, it has lower nutritional value than hay.

In agroforestry systems are developed to produce tree hay.

It is the leaf and seed material in the hay that determines its quality, because they contain more of the nutrition value for the animal than the stems do. Farmers try to harvest hay at the point when the seed heads are not quite ripe and the leaf is at its maximum when the grass is mowed in the field. The cut material is allowed to dry so that the bulk of the moisture is removed but the leafy material is still robust enough to be picked up from the ground by machinery and processed into storage in bales, stacks or pits. Methods of haymaking thus aim to minimize the shattering and falling away of the leaves during handling.

Hay production is highly sensitive to weather conditions, particularly during the harvest period. In drought conditions, both seed and leaf production are stunted, resulting in hay with a high ratio of dry, coarse stems that possess very low nutritional value. Conversely, excessively wet weather can cause cut hay to spoil in the field before it can be baled. Consequently, the primary challenge and risk for farmers in hay production is managing the weather, especially during the critical few weeks when the plants are at optimal maturity for harvesting. A lucky break in the weather often moves the haymaking tasks (such as mowing, tedding, and baling) to the top priority on the farm's to-do list. This is reflected in the idiom to make hay while the sun shines. Hay that was too wet at cutting may develop rot and mold after being baled, creating the potential for toxins to form in the feed, which could make the animals sick.

After harvest, hay also has to be stored in a manner to prevent it from getting wet. Mold and spoilage reduce nutritional value and may cause illness in animals. A symbiotic fungus in fescue may cause illness in horses and cattle.

The successful harvest of maximum yields of high-quality hay is entirely dependent on the coincident occurrence of optimum crop, field, and weather conditions. When this occurs, there may be a period of intense activity on the hay farm while harvest proceeds until weather conditions become unfavourable.

Use

Hay or grass is the foundation of the diet for all grazing animals, and can provide as much as 100% of the fodder required for an animal. Hay is usually fed to an animal during times when winter, drought, or other conditions make pasture unavailable. Animals that can eat hay vary in the types of grasses suitable for consumption, the ways they consume hay, and how they digest it. Therefore, different types of animals require hay that consists of similar plants to what they would eat while grazing, and, likewise, plants that are toxic to an animal in pasture are generally also toxic if they are dried into hay.

Most animals are fed hay in two daily feedings, morning and evening, more for the convenience of humans, as most grazing animals on pasture naturally consume fodder in multiple feedings throughout the day. Some animals, especially those being raised for meat, may be given enough hay that they simply are able to eat all day. Other animals, especially those that are ridden or driven as working animals may be given a more limited amount of hay to prevent them from getting too fat. The proper amount of hay and the type of hay required varies somewhat between different species. Some animals are also fed concentrated feeds such as grain or vitamin supplements in addition to hay. In most cases, hay or pasture forage must make up 50% or more of the diet by weight.

One of the most significant differences in hay digestion is between ruminant animals, such as cattle and sheep, and nonruminant, hindgut fermentors, such as horses. Both types of animals can digest cellulose in grass and hay, but do so by different mechanisms. Because of the four-chambered stomach of cattle, they are often able to break down older forage and have more tolerance of mold and changes in diet. The single-chambered stomach and cecum or "hindgut" of the horse uses bacterial processes to break down cellulose that are more sensitive to changes in feeds and the presence of mold or other toxins, requiring horses to be fed hay of a more consistent type and quality.

Different animals also use hay in different ways: cattle evolved to eat forages in relatively large quantities at a single feeding, and then, due to the process of rumination, take a considerable amount of time for their stomachs to digest food, often accomplished while the animal is lying down, at rest. Thus quantity of hay is important for cattle, who can effectively digest hay of low quality if fed in sufficient amounts. Sheep will eat between two and four percent of their body weight per day in dry feed, such as hay, and are very efficient at obtaining the most nutrition possible from three to five pounds per day of hay or other forage. They require three to four hours per day to eat enough hay to meet their nutritional requirements.

Unlike ruminants, horses digest food in small portions throughout the day, and can only use approximately 2.5% of their body weight in feed in any 24-hour period. They evolved to be continuously on the move while grazing (covering up to 50 mi per day in the wild) and their stomach digests food quite rapidly. Thus, they extract more nutrition out of smaller quantities of feed. When horses are fed low-quality hay, they may develop an unhealthy, obese, "hay belly" due to over-consumption of "empty" calories. If their type of feed is changed dramatically, or if they are fed moldy hay or hay containing toxic plants, they can become ill; colic is the leading cause of death in horses. Contaminated hay can also lead to respiratory problems in horses. Hay can be soaked in water, sprinkled with water or subjected to steaming to reduce dust.

Harvest and transport
Methods and the terminology to describe the steps of making hay have varied greatly throughout history, and many regional variations still exist today. Whether done by hand or by modern mechanized equipment, tall grass and legumes at the proper stage of maturity must be cut, then allowed to dry (preferably by the sun), then raked into long, narrow piles known as windrows. Next, the cured hay is gathered up in some form (usually by some type of baling process) and placed for storage into a haystack or into a barn or shed to protect it from moisture and rot.

During the growing season, which is spring and early summer in temperate climates, grass grows at a fast pace. Hay reaches its peak nutritional value when all leaves are fully developed and seed or flower heads are just shy of full maturity. At this stage of maximum growth in the pasture or field, if timed correctly, the hay is cut. Grass hay cut too early retains high moisture content, making it harder to cure and resulting in a lower yield per acre compared to more mature grass. However, hay cut too late becomes coarser, has a lower resale value, and loses some of its nutrients. Typically, there is a two-week "window" during which grass is at its ideal stage for harvesting hay. The time for cutting alfalfa hay is ideally done when plants reach maximum height and are producing flower buds or just beginning to bloom, cutting during or after full bloom results in lower nutritional value of the hay.

Hay can be raked into rows as it is cut, then turned periodically to dry, particularly if a modern swather is used. Or, especially with older equipment or methods, the hay is cut and allowed to lie spread out in the field until it is dry, then raked into rows for processing into bales afterwards. During the drying period, which can take several days, the process is usually sped up by turning the cut hay over with a hay rake or spreading it out with a tedder. If it rains while the hay is drying, turning the windrow can also allow it to dry faster. Turning the hay too often or too roughly can also cause drying leaf matter to fall off, reducing the nutrients available to animals. Drying can also be sped up by mechanized processes, such as the use of a hay conditioner, or by the use of chemicals sprayed onto the hay to speed evaporation of moisture, though these are more expensive techniques, not in general use except in areas where there is a combination of modern technology, high prices for hay, and too much rain for hay to dry properly.

Once hay is cut, dried and raked into windrows, it is usually gathered into bales or bundles, and then hauled to a central location for storage. In some places, depending on geography, region, climate, and culture, hay is gathered loose and stacked without being baled first.

Early methods

Columella in his De re rustica describes the usual haying process of the early Roman Empire.

Timothy grass and clover were the most common plants used for hay in the early 20th century in the United States, though both plants are native to Europe.

Much hay was originally cut by scythe by teams of workers, dried in the field and gathered loose on wagons. Later, haying was accomplished with horse-drawn implements such as mowers. With the invention of agricultural machinery such as the tractor and the baler, most hay production became mechanized by the 1930s.

After hay was cut and dried, it was raked or rowed up by raking it into a linear heap by hand or with a horse-drawn implement. Turning hay, when needed, originally was done by hand with a fork or rake. Once the dried hay was rowed up, pitchforks were used to pile it loose, originally onto a horse-drawn cart or wagon, later onto a truck or tractor-drawn trailer, for which a sweep could be used instead of pitch forks.

Loose hay was taken to an area designated for storage—usually a slightly raised area for drainage—and built into a haystack. The stack was made waterproof as it was built (a skilled task) and the hay would compress under its own weight and cure by the release of heat from the residual moisture in the hay and from the compression forces. The stack was fenced from the rest of the paddock in a rick yard, and often thatched or sheeted to keep it dry. When needed, slices of hay would be cut using a hay knife and fed to animals each day.

On some farms, the loose hay was stored in a barrack, shed, or barn, normally in such a way that it would compress down and cure. Hay could be stored in a specially designed barn with little internal structure to allow more room for the hay loft. Alternatively, an upper storey of a cow-shed or stable was used, with hatches in the floor to allow hay to be thrown down into hay-racks below. Depending on the region, the term "hay rick" could refer to the machine for cutting hay, the haystack or the wagon used to collect the hay.

Hay baling began with the invention of the first hay press in about 1850. Hay was baled for easier handling and to reduce space required for storage and shipment. The first bales weighed about 300 pounds. The original machines were of a vertical design similar to the one photographed by the Greene Co. Historical Society. They used a horse-driven screw-press mechanism or a dropped weight to compress the hay. The first patent went to HL Emery for a horse-powered, screw-operated hay press in 1853. Other models were reported as early as 1843 built by PK Dederick's Sons of Albany, New York, or Samuel Hewitt of Switzerland County, Indiana. Later, horizontal machines were devised. One was the “Perpetual Press” made by PK Dederick of Albany in 1872. They could be powered by steam engines by about 1882. The continuous hay baler arrived in 1914.

Modern mechanized techniques

Modern mechanized hay production today is usually performed by a number of machines. While small operations use a tractor to pull various implements for mowing and raking, larger operations use specialized machines such as a mower or a swather, which are designed to cut the hay and arrange it into a windrow in one step. Balers are usually pulled by a tractor, with larger balers requiring more powerful tractors.

Mobile balers, machines that gather and bale hay in one process were first developed around 1940. The initial balers produced rectangular bales that were small enough for an individual to lift, typically weighing between 70 and 100 pounds (32 to 45 kg) each. The size and shape of these bales allowed for manual handling, including lifting, stacking on transport vehicles, and constructing a haystack by hand. To reduce labor and enhance safety, loaders and stackers were subsequently developed to mechanize the transportation of small bales from the field to the haystack or hay barn. Later in the 20th century, balers were developed capable of producing large bales that weigh up to 3000 lb.

Conditioning of hay crop during cutting or soon thereafter is popular. The basic idea is that it decreases drying time, particularly in humid climates or if rain threatens to interfere with haying. Usually, rollers or flails inside a mower conditioner crimp, crack or strip the alfalfa or grass stems to increase evaporation rate. Sometimes, a salt solution is sprayed over the top of the hay (generally alfalfa) that helps to dry the hay.

Fertilization and weed control
Modern hay production often relies on artificial fertilizer and herbicides. Traditionally, manure has been used on hayfields, but modern chemical fertilizers are used today as well. Hay that is to be certified as weed-free for use in wilderness areas must often be sprayed with chemical herbicides to keep unwanted weeds from the field, and sometimes even non-certified hayfields are sprayed to limit the production of noxious weeds. Organic forms of fertilization and weed control are required for hay grown for consumption by animals whose meat will ultimately be certified organic. To that end, compost and field rotation can enhance soil fertility, and regular mowing of fields in the growth phase of the hay will often reduce the prevalence of undesired weeds. In recent times, some producers have experimented with human sewage sludge to grow hay. This is not a certified organic method and no warning labels are mandated by EPA. One concern with hay grown on human sewage sludge is that the hay can take up heavy metals, which are then consumed by animals. Molybdenum poisoning is a particular concern in ruminants such as cows and goats, and there have been animal deaths. Another concern is with a herbicide known as aminopyralid, which can pass through the digestive tract in animals, making their resulting manure toxic to many plants and thus unsuitable as fertilizer for food crops. Aminopyralid and related herbicides can persist in the environment for several years.

Baling

Small square bales are made in two main variations. The smaller "two tie" (two twines to hold the bale together) or larger "three-tie" (three twines to hold the bale together). They vary in size within both groups but are generally popular in different markets. The smaller two-tie bales are favored in the hobby animal market and are preferred for their convenient size. The larger, three-tie bales are favored by producers wanting to export bales because of the increase of efficiency in transportation and also by customers for a better price per ton. The two-tie small bales are the original form factor of hay bales. Balers for both types of small bales are still manufactured, as well as stackers, bundlers and bale accumulators for handling them. There are also some farms that still use equipment manufactured over 50 years ago to produce small bales. The small bale remains part of overall ranch lore and tradition with "hay bucking" competitions still held for fun at many rodeos and county fairs. Small square bales are often stacked mechanically or by hand in a crisscrossed fashion sometimes called a "haystack", "rick" or "hayrick". Rain tends to wash nutrition out of hay and can cause spoilage or mold; hay in small square bales is particularly susceptible to this. Small bales are therefore often stored in a haymow or hayshed. Haystacks built outside are often protected by tarpaulins. If this is not done, the top two layers of the stack are often lost to rot and mold, and if the stack is not arranged in a proper haystack, moisture can seep even deeper into the stack. The rounded shape and tighter compaction of round bales make them less susceptible to spoilage, as the water is less likely to penetrate into the bale. The addition of net wrap, which is not used on square bales, offers even greater weather resistance. People who keep small numbers of animals may prefer small bales that can be handled by one person without machinery. There is also a risk that hay bales may be moldy, or contain decaying carcasses of small creatures that were accidentally killed by baling equipment and swept up into the bale, which can produce toxins such as botulinum toxin. Both can be deadly to non-ruminant herbivores, such as horses, and when this occurs, the entire contaminated bale generally is thrown out, another reason some people continue to support the market for small bales.

Farmers who need to make large amounts of hay are likely to choose balers that produce much larger bales, maximizing the amount of hay that is protected from the elements. Large bales come in two types, round and square. Large square bales, which can weigh up to 1000 kg, can be stacked and are easier to transport on trucks. Large round bales, which typically weigh 300 to(-), are more moisture-resistant, and pack the hay more densely (especially at the center). Round bales are quickly fed with the use of mechanized equipment. The ratio of volume to surface area makes it possible for many dry-area farmers to leave large bales outside until they are consumed. Wet-area farmers and those in climates with heavy snowfall can stack round bales under a shed or tarp, but can also use a light but durable plastic wrap that partially encloses bales left outside. The wrap repels moisture but leaves the ends of the bale exposed so that the hay itself can "breathe" and does not begin to ferment. When it is possible to store round bales under a shed, they last longer and less hay is lost to rot and moisture.

For animals that eat silage, a bale wrapper may be used to seal a round bale completely and trigger the fermentation process. It is a technique used as a money-saving process by producers who do not have access to a superior silo, and for producing silage that is transported to other locations. In very damp climates, it is a legitimate alternative to drying hay completely and when processed properly, the natural fermentation process prevents mold and rot. Round bale silage is also sometimes called "haylage", and is seen more commonly in Europe than in either the United States or Australia. Hay stored in this fashion must remain completely sealed in plastic, as any holes or tears will allow the entrance of oxygen and can stop the preservation properties of fermentation and lead to spoilage.

Stacking

Hay requires protection from the weather, and is optimally stored inside buildings, but weather protection is also provided in other ways involving outdoor storage, either in haystacks or in large tight bales (round or rectangular); these methods all depend on the surface of an outdoor mass of hay (stack or bale) taking the hit of the weather and thereby preserving the main body of hay underneath.

Traditionally, outdoor hay storage was done with haystacks of loose hay, where most of the hay was sufficiently preserved to last through the winter, and the top surface of the stack (being weathered) was consigned to become compost the next summer. The term "loose" means not pressed or baled but does not necessarily mean a light, fluffy lay of randomly oriented stems. Especially in wet climates, such as those of Britain, the degree of shedding of rainwater by the stack's outer surface is an important factor, and the stacking of loose hay was developed into a skilled-labor task that in its more advanced forms even involved thatching the top. In many stacking methods (with or without thatched tops), stems were oriented in sheaves, which were laid in oriented sequence.

With the advent of large bales since the 1960s, today hay is often stored outdoors because the outer surface of the large bale performs the weather-shedding function. The large bales can also be stacked, which allows a given degree of exposed surface area to count for a larger volume of protected interior hay. Plastic tarpaulins are sometimes used to shed the rain, with the goal of reduced hay wastage, but the cost of the tarpaulins must be weighed against the cost of the hay spoilage percentage difference; it may not be worth the cost, or the plastic's environmental footprint.

After World War II, British farmers found that the demand outstripped supply for skilled farm laborers experienced in the thatching of haystacks. This no doubt contributed to the pressure for baling in large bales to increasingly replace stacking, which was happening anyway as haymaking technology (like other farm technology) continued toward extensive mechanization with one-person operation of many tasks. Today tons of hay can be cut, conditioned, dried, raked, and baled by one person, as long as the right equipment is at hand (although that equipment is expensive). These tons of hay can also be moved by one person, again with the right (expensive) equipment, as loaders with long spikes run by hydraulic circuits pick up each large bale and move it to its feeding location.

A fence may be built to enclose a haystack and prevent roaming animals from eating it, or animals may feed directly from a field-constructed stack as part of their winter feeding.

Haystacks are also sometimes called haycocks; among some users this term refers more specifically to small piles of cut-and-gathered hay awaiting stacking into larger stacks. The words (haystack, haycock) are usually styled as solid compounds, but not always. Haystacks are also sometimes called stooks, shocks, or ricks.

Loose stacks are built to prevent the accumulation of moisture and promote drying or curing. In some places, this is accomplished by constructing stacks with a conical or ridged top. The exterior may look gray on the surface after weathering, but the inner hay retains traces of its fresh-cut aroma and maintains a faded green tint. They can be covered with thatch, or kept within a protective structure. One such structure is a moveable roof supported by four posts, historically called a Dutch roof, hay barrack, or hay cap. Haystacks may also be built on top of a foundation laid on the ground to reduce spoilage, in some places made of wood or brush. In other areas, hay is stacked loose, built around a central pole, a tree, or within an area of three or four poles to add stability to the stack.

One loose hay stacking technique seen in the British Isles is to initially stack freshly cut hay into smaller mounds called foot cocks, hay coles, kyles, hayshocks or haycocks, to facilitate initial curing. These are sometimes built atop platforms or tripods formed of three poles, used to keep hay off the ground and let air into the center for better drying. The shape causes dew and rainwater to roll down the sides, allowing the hay within to cure. People who handle the hay may use hayforks or pitchforks to move or pitch the hay in building haycocks and haystacks. Construction of tall haystacks is sometimes aided with a ramp, ranging from simple poles to a device for building large loose stacks called a beaverslide.

Mold

Hay is generally one of the safest feeds to provide to domesticated grazing herbivores. Amounts must be monitored so animals do not get too fat or too thin. Supplemental feed may be required for working animals with high energy requirements.

Animals who eat spoiled hay may develop a variety of illnesses, from coughs related to dust and mold, to various other illnesses, the most serious of which may be botulism, which can occur if a small animal, such as a rodent or snake, is killed by the baling equipment, then rots inside the bale, causing a toxin to form. Some animals are sensitive to particular fungi or molds that may grow on living plants. For example, an endophytic fungus that sometimes grows on fescue can cause abortion in pregnant mares. Some plants themselves may also be toxic to some animals. For example, Pimelea, a native Australian plant, also known as flax weed, is highly toxic to cattle.

Farmer's lung is a hypersensitivity pneumonitis induced by the inhalation of biologic dusts coming from hay dust or mold spores or other agricultural products. Exposure to hay can also trigger allergic rhinitis for people who are hypersensitive to airborne allergens.

Spontaneous combustion
Hay must be fully dried when baled and kept dry in storage. If hay is baled while too moist or becomes wet while in storage, there is a significant risk of spontaneous combustion. Hay stored outside must be stacked in such a way that moisture contact is minimal. Some stacks are arranged in such a manner that the hay itself sheds water when it falls. Other methods of stacking use the first layers or bales of hay as a cover to protect the rest. To completely keep out moisture, outside haystacks can also be covered by tarps, and many round bales are partially wrapped in plastic as part of the baling process. Hay is also stored under a roof when resources permit. It is frequently placed inside sheds, or stacked inside of a barn. On the other hand, care must also be taken that hay is never exposed to any possible source of heat or flame, as dry hay and the dust it produces are highly flammable.

Hay baled before it is fully dry can produce enough heat to start a fire. Haystacks produce internal heat due to bacterial fermentation. If hay is stacked with wet grass, the heat produced can be sufficient to ignite the hay causing a fire. Farmers have to be careful about moisture levels to avoid spontaneous combustion, which is a leading cause of haystack fires. Heat is produced by the respiration process, which occurs until the moisture content of drying hay drops below 40%. Hay is considered fully dry when it reaches 20% moisture. Combustion problems typically occur within five to seven days of baling. A bale cooler than 120 F is in little danger, but bales between 120 and 140 F need to be removed from a barn or structure and separated so that they can cool off. If the temperature of a bale exceeds more than 140 F, it can combust.

To check hay moisture content, the farmer can use a hand, an oven or a moisture tester. The most efficient way is to use a moisture tester which shows the moisture content in a few seconds.

Weight

Due to its weight, hay can cause a number of injuries to humans, particularly those related to lifting and moving bales, as well as risks related to stacking and storing. Hazards include the danger of having a poorly constructed stack collapse, causing either falls to people on the stack or injuries to people on the ground who are struck by falling bales. Large round hay bales present a particular danger to those who handle them, because they can weigh over 1000 lb and cannot be moved without special equipment. Nonetheless, because they are cylindrical in shape, and thus can roll easily, it is not uncommon for them to fall from stacks or roll off the equipment used to handle them. From 1992 to 1998, 74 farm workers in the United States were killed in large round hay bale accidents, usually when bales were being moved from one location to another, such as when feeding animals.

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Straw

Straw is an agricultural byproduct consisting of the dry stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the yield by weight of cereal crops such as barley, oats, rice, rye and wheat. It has a number of different uses, including fuel, livestock bedding and fodder, thatching and basket making.

Straw is usually gathered and stored in a straw bale, which is a bale, or bundle, of straw tightly bound with twine, wire, or string. Straw bales may be square, rectangular, star shaped or round, and can be very large, depending on the type of baler used.

Uses
Current and historic uses of straw include:

Animal feed

Straw may be fed as part of the roughage component of the diet to cattle or horses that are on a near maintenance level of energy requirement. It has a low digestible energy and nutrient content (as opposed to hay, which is much more nutritious). The heat generated when microorganisms in a herbivore's gut digest straw can be useful in maintaining body temperature in cold climates. Due to the risk of impaction and its poor nutrient profile, it should always be restricted to part of the diet. It may be fed as it is, or chopped into short lengths, known as chaff.

Basketry
Bee skeps and linen baskets are made from coiled and bound together continuous lengths of straw. The technique is known as lip work.

Bedding
Straw is commonly used as bedding for ruminants and horses. It may be used as bedding and food for small animals, but this often leads to injuries to mouth, nose and eyes as straw is quite sharp.

The straw-filled mattress, also known as a palliasse, is still used by people in many parts of the world.

Bioplastic
Rice straw, an agricultural waste which is not usually recovered, can be turned into bioplastic with mechanical properties akin to polystyrene in its dry state.

Chemicals
Straw is being investigated as a source of fine chemicals including alkaloids, flavonoids, lignins, phenols, and steroids.

Construction material
In many parts of the world, straw is used to bind clay and concrete. A mixture of clay and straw, known as cob, can be used as a building material. There are many recipes for making cob.

When baled, straw has moderate insulation characteristics (about R-1.5/inch according to Oak Ridge National Lab and Forest Product Lab testing). It can be used, alone or in a post-and-beam construction, to build straw bale houses. When bales are used to build or insulate buildings, the straw bales are commonly finished with earthen plaster. The plastered walls provide some thermal mass, compressive and ductile structural strength, and acceptable fire resistance as well as thermal resistance (insulation), somewhat in excess of North American building code. Straw is an abundant agricultural waste product, and requires little energy to bale and transport for construction. For these reasons, straw bale construction is gaining popularity as part of passive solar and other renewable energy projects.

Wheat straw can be used as a fibrous filler combined with polymers to produce composite lumber.

Enviroboard can be made from straw.

Strawblocks are strawbales that have been recompressed to the density of woodblocks, for compact cargo container shipment, or for straw-bale construction of load-bearing walls that support roof-loads, such as a "living" or green roofs.

Crafts
Craft usages of straw include:
 * Corn dollies
 * Himmeli (straw art)
 * Straw marquetry
 * Straw painting
 * Straw plaiting
 * Scarecrows
 * Japanese Traditional Cat's House
 * Japanese wara art

Construction site sediment control
Straw bales are sometimes used for sediment control at construction sites. However, bales are often ineffective in protecting water quality and are maintenance-intensive. For these reasons the U.S. Environmental Protection Agency (EPA) and various state agencies recommend use of alternative sediment control practices where possible, such as silt fences, fiber rolls and geotextiles.

They can also be used as burned area emergency response, as ground cover or as in-stream check dams.

Fuel source
The use of straw as a carbon-neutral energy source is increasing rapidly, especially for biobutanol. Straw or hay briquettes are a biofuel substitute to coal.

Straw, processed first as briquettes, has been fed into a biogas plant in Aarhus University, Denmark, in a test to see if higher gas yields could be attained.

The use of straw in large-scale biomass power plants is becoming mainstream in the EU, with several facilities already online. The straw is either used directly in the form of bales, or densified into pellets which allows for the feedstock to be transported over longer distances. Finally, torrefaction of straw with pelletisation is gaining attention, because it increases the energy density of the resource, making it possible to transport it still further. This processing step also makes storage much easier, because torrefied straw pellets are hydrophobic. Torrefied straw in the form of pellets can be directly co-fired with coal or natural gas at very high rates and make use of the processing infrastructures at existing coal and gas plants. Because the torrefied straw pellets have superior structural, chemical and combustion properties to coal, they can replace all coal and turn a coal plant into an entirely biomass-fed power station. First generation pellets are limited to a co-firing rate of 15% in modern IGCC plants.

Gardening
Straw bale gardening is also popular among gardeners who do not have enough space for soil gardening. When properly conditioned, straw bales can be used as a perfect soil substitute.

Hats
There are several styles of straw hats that are made of woven straw.

Many thousands of women and children in England (primarily in the Luton district of Bedfordshire), and large numbers in the United States (mostly Massachusetts), were employed in plaiting straw for making hats. By the late 19th century, vast quantities of plaits were being imported to England from Canton in China, and in the United States most of the straw plait was imported.

A fiber analogous to straw is obtained from the plant Carludovica palmata, and is used to make Panama hats.

Traditional Japanese rain protection consisted of a straw hat and a mino cape.

Horticulture
Straw is used in cucumber houses and for mushroom growing.

In Japan, certain trees are wrapped with straw to protect them from the effects of a hard winter as well as to use them as a trap for parasite insects. (see Komomaki)

It is also used in ponds to reduce algae by changing the nutrient ratios in the water.

The soil under strawberries is covered with straw to protect the ripe berries from dirt, and straw is also used to cover the plants during winter to prevent the cold from killing them.

Straw also makes an excellent mulch.

Packaging
Straw is resistant to being crushed and therefore makes a good packing material. A company in France makes a straw mat sealed in thin plastic sheets.

Straw envelopes for wine bottles have become rarer, but are still to be found at some wine merchants.

Wheat straw is also used in compostable food packaging such as compostable plates. Packaging made from wheat straw can be certified compostable and will biodegrade in a commercial composting environment.

Paper
Straw can be pulped to make paper.

Rope
Rope made from straw was used by thatchers, in the packaging industry and even in iron foundries.

Saekki is a traditional Korean rope made of woven straw.

Shoes
The Chinese wore cailu or caixie, shoes and sandals made of straw, well into modernity.

Koreans wear jipsin, sandals made of straw.

Several types of traditional Japanese shoes, such as waraji and zōri, are made of straw.

In some parts of Germany like Black Forest and Hunsrück people wear straw shoes at home or at carnival.

Targets
Heavy-gauge straw rope is coiled and sewn tightly together to make archery targets. This is no longer done entirely by hand, but is partially mechanised. Sometimes a paper or plastic target is set up in front of straw bales, which serve to support the target and provide a safe backdrop.

Thatching
Thatching uses straw, reed or similar materials to make a waterproof, lightweight roof with good insulation properties. Straw for this purpose (often wheat straw) is grown specially and harvested using a reaper-binder.

Health and safety
Dried straw presents a fire hazard that can ignite easily if exposed to sparks or an open flame. It can also trigger allergic rhinitis in people who are hypersensitive to airborne allergens such as straw dust.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Straw


text:
Loom

A loom is a device used to weave cloth and tapestry. The basic purpose of any loom is to hold the warp threads under tension to facilitate the interweaving of the weft threads. The precise shape of the loom and its mechanics may vary, but the basic function is the same.

Etymology and usage
The word "loom" derives from the Old English geloma, formed from ge- (perfective prefix) and loma, a root of unknown origin; the whole word geloma meant a utensil, tool, or machine of any kind. In 1404 "lome" was used to mean a machine to enable weaving thread into cloth. By 1838 "loom" had gained the additional meaning of a machine for interlacing thread.

Basic structure
Weaving is done on two sets of threads or yarns, which cross one another. The warp threads are the ones stretched on the loom (from the Proto-Indo-European *werp, "to bend" ). Each thread of the weft (i.e. "that which is woven") is inserted so that it passes over and under the warp threads.

The ends of the warp threads are usually fastened to beams. One end is fastened to one beam, the other end to a second beam, so that the warp threads all lie parallel and are all the same length. The beams are held apart to keep the warp threads taut.

The textile is woven starting at one end of the warp threads, and progressing towards the other end. The beam on the finished-fabric end is called the cloth beam. The other beam is called the warp beam.

Beams may be used as rollers to allow the weaver to weave a piece of cloth longer than the loom. As the cloth is woven, the warp threads are gradually unrolled from the warp beam, and the woven portion of the cloth is rolled up onto the cloth beam (which is also called the takeup roll). The portion of the fabric that has already been formed but not yet rolled up on the takeup roll is called the fell.

Not all looms have two beams. For instance, warp-weighted looms have only one beam; the warp yarns hang from this beam. The bottom ends of the warp yarns are tied to dangling loom weights.

Motions
A loom has to perform three principal motions: shedding, picking, and battening.

 * Shedding. Shedding is pulling part of the warp threads aside to form a shed (the space between the raised and unraised warp yarns). The shed is the space through which the filling yarn, carried by the shuttle, can be inserted, forming the weft.
 * Sheds may be simple: for instance, lifting all the odd threads and all the even threads alternately produces a tabby weave (the two sheds are called the shed and countershed). More intricate shedding sequences can produce more complex weaves, such as twill.
 * Picking. A single crossing of the weft thread from one side of the loom to the other, through the shed, is known as a pick. Picking is passing the weft through the shed. A new shed is then formed before a new pick is inserted.
 * Conventional shuttle looms can operate at speeds of about 150 to 160 picks per minute.
 * Battening. After the pick, the new pass of weft thread has to be tamped up against the fell, to avoid making a fabric with large, irregular gaps between the weft threads. This compression of the weft threads is called battening.

There are also usually two secondary motions, because the newly constructed fabric must be wound onto cloth beam. This process is called taking up. At the same time, the warp yarns must be let off or released from the warp beam, unwinding from it. To become fully automatic, a loom needs a tertiary motion, the filling stop motion. This will brake the loom if the weft thread breaks. An automatic loom requires 0.125 hp to 0.5 hp to operate.

Components
A loom, then, usually needs two beams, and some way to hold them apart. It generally has additional components to make shedding, picking, and battening faster and easier. There are also often components to help take up the fell.

The nature of the loom frame and the shedding, picking, and battening devices vary. Looms come in a wide variety of types, many of them specialized for specific types of weaving. They are also specialized for the lifestyle of the weaver. For instance, nomadic weavers tend to use lighter, more portable looms, while weavers living in cramped city dwellings are more likely to use a tall upright loom, or a loom that folds into a narrow space when not in use.

Frames
Loom frames can be roughly divided, by the orientation of the warp threads, into horizontal looms and vertical looms. There are many finer divisions. Most handlooom frame designs can be constructed fairly simply.

Backstrap loom
The back-strap loom (also known as belt loom) is a simple loom with ancient roots, still used in many cultures around the world (such as Andean textiles). It consists of two sticks or bars between which the warps are stretched. One bar is attached to a fixed object and the other to the weaver, usually by means of a strap around the weaver's back. The weaver leans back and uses their body weight to tension the loom.

Both simple and complex textiles can be woven on backstrap looms. They produce narrowcloth: width is limited to the weaver's armspan. They can readily produce warp-faced textiles, often decorated with intricate pick-up patterns woven in complementary and supplementary warp techniques, and brocading. Balanced weaves are also possible on the backstrap loom.

Warp-weighted loom

The warp-weighted loom is a vertical loom that may have originated in the Neolithic period. Its defining characteristic is hanging weights (loom weights) which keep bundles of the warp threads taut. Frequently, extra warp thread is wound around the weights. When a weaver has woven far enough down, the completed section (fell) can be rolled around the top beam, and additional lengths of warp threads can be unwound from the weights to continue. This frees the weaver from vertical size constraint. Horizontally, breadth is limited by armspan; making broadwoven cloth requires two weavers, standing side by side at the loom.

Simple weaves, and complex weaves that need more than two different sheds, can both be woven on a warp-weighted loom. They can also be used to produce tapestries.

Pegged or floor loom

In pegged looms, the beams can be simply held apart by hooking them behind pegs driven into the ground, with wedges or lashings used to adjust the tension. Pegged looms may, however, also have horizontal sidepieces holding the beams apart.

Such looms are easy to set up and dismantle, and are easy to transport, so they are popular with nomadic weavers. They are generally only used for comparatively small woven articles. Urbanites are unlikely to use horizontal floor looms as they take up a lot of floor space, and full-time professional weavers are unlikely to use them as they are unergonomic. Their cheapness and portability is less valuable to urban professional weavers.

Treadle loom
In a treadle loom, the shedding is controlled by the feet, which tread on the treadles.

The earliest evidence of a horizontal loom is found on a pottery dish in ancient Egypt, dated to 4400 BC. It was a frame loom, equipped with treadles to lift the warp threads, leaving the weaver's hands free to pass and beat the weft thread.

A pit loom has a pit for the treadles, reducing the stress transmitted through the much shorter frame.

In a wooden vertical-shaft loom, the heddles are fixed in place in the shaft. The warp threads pass alternately through a heddle, and through a space between the heddles (the shed), so that raising the shaft raises half the threads (those passing through the heddles), and lowering the shaft lowers the same threads — the threads passing through the spaces between the heddles remain in place.

A treadle loom for figured weaving may have a large number of harnesses or a control head. It can, for instance, have a Jacquard machine attached to it.

Tapestry looms
Tapestry can have extremely complex wefts, as different strands of wefts of different colours are used to form the pattern. Speed is lower, and shedding and picking devices may be simpler. Looms used for weaving traditional tapestry are called not as "vertical-warp" and "horizontal-warp", but as "high-warp" or "low-warp" (the French terms haute-lisse and are also used in English).

Ribbon, Band, and Inkle weaving
Inkle looms are narrow looms used for narrow work. They are used to make narrow warp-faced strips such as ribbons, bands, or tape. They are often quite small; some are used on a tabletop. others are backstraps looms with a rigid heddle, and very portable.

Darning looms
There exist very small hand-held looms known as darning looms. They are made to fit under the fabric being mended, and are often held in place by an elastic band on one side of the cloth and a groove around the loom's darning-egg portion on the other. They may have heddles made of flip-flopping rotating hooks. Other devices sold as darning looms are just a darning egg and a separate comb-like piece with teeth to hook the warp over; these are used for repairing knitted garments and are like a linear knitting spool. Darning looms were sold during World War Two clothing rationing in the United Kingdom and Canada, and some are homemade.

Circular handlooms
Circular looms are used to create seamless tubes of fabric for products such as hosiery, sacks, clothing, fabric hoses (such as fire hoses) and the like. Tablet weaving can be used to knit tubes, including tubes that split and join.

Small jigs also used for circular knitting are also sometimes called circular looms, but they are used for knitting, not weaving.

Shedding methods

It is possible to weave by manually threading the weft over and under the warp threads, but this is slow. Some tapestry techniques use manual shedding. Pin looms and peg looms also generally have no shedding devices. Pile carpets generally do not use shedding for the pile, because each pile thread is individually knotted onto the warps, but there may be shedding for the weft holding the carpet together.

Usually weaving uses shedding devices. These devices pull some of the warp threads to each side, so that a shed is formed between them, and the weft is passed through the shed. There are a variety of methods for forming the shed. At least two sheds must be formed, the shed and the countershed. Two sheds is enough for tabby weave; more complex weaves, such as twill weaves, satin weaves, diaper weaves, and figured (picture-forming) weaves, require more sheds.

Shed-rod
A shed-rod (shedding stick, shed roll) is simply a stick woven through the warp threads. When pulled perpendicular to the threads (or rotated to stand on edge, for wide, flat shedding rods), it creates a shed. To create the counter-shed, a heddle-bar is usually used.

Heddle-bar
A heddle-bar is simply a stick placed across the warp and tied to individual warp threads. When it is lifted, it pulls the warp threads it is tied to out of position, creating a shed.

A warp-weighted loom (see diagram) typically uses a heddle-bar. It has two upright posts (C); they support a horizontal beam (D), which is cylindrical so that the finished cloth can be rolled around it, allowing the loom to be used to weave a piece of cloth taller than the loom, and preserving an ergonomic working height. The warp threads (F, and A and B) hang from the beam and rest against the shed rod (E). The heddle-bar (G) is tied to some of the warp threads (A, but not B), using loops of string called leashes (H). So when the heddle rod is pulled out and placed in the forked sticks protruding from the posts (not lettered, no technical term given in citation), the shed (1) is replaced by the counter-shed (2). By passing the weft through the shed and the counter-shed, alternately, cloth is woven.

Heddle-rods are used on modern tapestry looms.

Tablet weaving
Tablet weaving uses cards punched with holes. The warp threads pass through the holes, and the cards are twisted and shifted to created varied sheds. This shedding technique is used for narrow work. It is also used to finish edges, weaving decorative selvage bands instead of hemming.

Rotating-hook heddles
There are heddles made of flip-flopping rotating hooks, which raise and lower the warp, creating sheds. The hooks, when vertical, have the weft threads looped around them horizontally. If the hooks are flopped over on side or another, the loop of weft twists, raising one or the other side of the loop, which creates the shed and countershed.

Rigid heddles

Rigid heddles are generally used on single-shaft looms. Odd warp threads go through the slots, and even ones through the circular holes, or vice-versa. The shed is formed by lifting the heddle, and the countershed by depressing it. The warp threads in the slots stay where they are, and the ones in the circular holes are pulled back and forth. A single rigid heddle can hold all the warp threads, though sometimes multiple rigid heddles are used.

Treadles may be used to drive the rigid heddle up and down.

Multiple heddles

Rigid heddles (above) are called "rigid" to distinguish them from string and metal heddles, where each warp thread has its own heddle, which has an eye at each end and one in the middle for the warp thread. The eyes in the ends are fastened to a shaft, all in a row. This requires multiple shafts; it cannot be done on a single-shaft loom. The different shafts (also called harnesses) must be controlled by some mechanism.

While non-rigid heddles generally mean that two shafts are needed even for a plain tabby weave, twill weaves require three or more (depending on the type of twill), and more complex figured weaves require still more harnesses.

Treadle-controlled looms
Treadle looms can control multiple harnessess with multiple treadles. The weaver selects which harnesses are engaged with their feet. One treadle may be connected to more than one harness, and any number of treadles can be engaged at once, meaning that the number of different sheds that can be selected is two to the power of the number of treadles. Eight is a large but reasonable number of treadles, giving a maximum of 28=256 sheds (some of which will not have enough threads on one side to be useful). The weaver must remember the sequence of treadling needed to produce the pattern.

Figure harness and the drawloom
A drawloom is for weaving figured cloth. In a drawloom, a "figure harness" is used to control each warp thread separately, allowing very complex patterns. A drawloom requires two operators, the weaver, and an assistant called a "drawboy" to manage the figure harness.

The earliest confirmed drawloom fabrics come from the State of Chu and date c. 400 BC. Some scholars speculate an independent invention in ancient Syria, since drawloom fabrics found in Dura-Europas are thought to date before 256 AD. The draw loom was invented in China during the Han dynasty (State of Liu?); foot-powered multi-harness looms and jacquard looms were used for silk weaving and embroidery, both of which were cottage industries with imperial workshops. The drawloom enhanced and sped up the production of silk and played a significant role in Chinese silk weaving. The loom was introduced to Persia, India, and Europe.

Dobby head

A dobby head is a device that replaces the drawboy, the weaver's helper who used to control the warp threads by pulling on draw threads. "Dobby" is a corruption of "draw boy". Mechanical dobbies pull on the draw threads using pegs in bars to lift a set of levers. The placement of the pegs determines which levers are lifted. The sequence of bars (they are strung together) effectively remembers the sequence for the weaver. Computer-controlled dobbies use solenoids instead of pegs.

Jacquard head
The Jacquard loom is a mechanical loom, invented by Joseph Marie Jacquard in 1801, which simplifies the process of manufacturing figured textiles with complex patterns such as brocade, damask and matelasse. The loom is controlled by punched cards with punched holes, each row of which corresponds to one row of the design. Multiple rows of holes are punched on each card and the many cards that compose the design of the textile are strung together in order. It is based on earlier inventions by the Frenchmen Basile Bouchon (1725), Jean Baptiste Falcon (1728) and Jacques Vaucanson (1740). To call it a loom is a misnomer, a Jacquard head could be attached to a power loom or a handloom, the head controlling which warp thread was raised during shedding. Multiple shuttles could be used to control the colour of the weft during picking. The Jacquard loom is the predecessor to the computer punched card readers of the 19th and 20th centuries.

Picking (weft insertion)

The weft may be passed across the shed as a ball of yarn, but usually this is too bulky and unergonomic. Shuttles are designed to be slim, so they pass through the shed; to carry a lot of yarn, so the weaver does not need to refill them too often; and to be an ergonomic size and shape for the particular weaver, loom, and yarn. They may also be designed for low friction.

Unnotched stick shuttles
At their simplest, these are just sticks wrapped with yarn. They may be specially shaped, as with the bobbins and bones used in tapestry-making (bobbins are used on vertical warps, and bones on horizontal ones).

Boat shuttles
Boat shuttles may be closed (central hollow with a solid bottom) or open (central hole goes right through). The yarn may be side-feed or end-feed. They are commonly made for 10-cm (4-inch) and 15-cm (6-inch) bobbin lengths.

Flying shuttle
Hand weavers who threw a shuttle could only weave a cloth as wide as their armspan. If cloth needed to be wider, two people would do the task (often this would be an adult with a child). John Kay (1704–1779) patented the flying shuttle in 1733. The weaver held a picking stick that was attached by cords to a device at both ends of the shed. With a flick of the wrist, one cord was pulled and the shuttle was propelled through the shed to the other end with considerable force, speed and efficiency. A flick in the opposite direction and the shuttle was propelled back. A single weaver had control of this motion but the flying shuttle could weave much wider fabric than an arm's length at much greater speeds than had been achieved with the hand thrown shuttle.

The flying shuttle was one of the key developments in weaving that helped fuel the Industrial Revolution. The whole picking motion no longer relied on manual skill and it was just a matter of time before it could be powered by something other than a human.

Weft insertion in power looms
Different types of power looms are most often defined by the way that the weft, or pick, is inserted into the warp. Many advances in weft insertion have been made in order to make manufactured cloth more cost effective. Weft insertion rate is a limiting factor in production speed. , industrial looms can weave at 2,000 weft insertions per minute.

There are five main types of weft insertion and they are as follows:
 * Shuttle: The first-ever powered looms were shuttle-type looms. Spools of weft are unravelled as the shuttle travels across the shed. This is very similar to projectile methods of weaving, except that the weft spool is stored on the shuttle. These looms are considered obsolete in modern industrial fabric manufacturing because they can only reach a maximum of 300 picks per minute.
 * Air jet: An air-jet loom uses short quick bursts of compressed air to propel the weft through the shed in order to complete the weave. Air jets are the fastest traditional method of weaving in modern manufacturing and they are able to achieve up to 1,500 picks per minute. However, the amounts of compressed air required to run these looms, as well as the complexity in the way the air jets are positioned, make them more costly than other looms.
 * Water jet: Water-jet looms use the same principle as air-jet looms, but they take advantage of pressurized water to propel the weft. The advantage of this type of weaving is that water power is cheaper where water is directly available on site. Picks per minute can reach as high as 1,000.
 * Rapier loom: This type of weaving is very versatile, in that rapier looms can weave using a large variety of threads. There are several types of rapiers, but they all use a hook system attached to a rod or metal band to pass the pick across the shed. These machines regularly reach 700 picks per minute in normal production.
 * Projectile: Projectile looms utilize an object that is propelled across the shed, usually by spring power, and is guided across the width of the cloth by a series of reeds. The projectile is then removed from the weft fibre and it is returned to the opposite side of the machine so it can be reused. Multiple projectiles are in use in order to increase the pick speed. Maximum speeds on these machines can be as high as 1,050 ppm.
 * Circular: Modern circular looms use up to ten shuttles, driven in a circular motion from below by electromagnets, for the weft yarns, and cams to control the warp threads. The warps rise and fall with each shuttle passage, unlike the common practice of lifting all of them at once. Circular looms are used to create seamless tubes of fabric for products such as hosiery, sacks, clothing, fabric hoses (such as fire hoses) and the like.

Battening
The newest weft thread must be beaten against the fell. Battening can be done with a long stick placed in the shed parallel to the weft (a sword batten), a shorter stick threaded between the warp threads perpendicular to warp and weft (a pin batten), a comb, or a reed (a comb with both ends closed, so that it has to be sleyed, that is have the warp threads threaded through it, when the loom is warped). For rigid-heddle looms, the heddle may be used as a reed.

Dandy mechanism
Patented in 1802, dandy looms automatically rolled up the finished cloth, keeping the fell always the same length. They significantly speeded up hand weaving (still a major part of the textile industry in the 1800s). Similar mechanisms were used in power looms.

Temples

The temples act to keep the cloth from shrinking sideways as it is woven. Some warp-weighted looms had temples made of loom weights, suspended by strings so that they pulled the cloth breadthwise. Other looms may have temples tied to the frame, or temples that are hooks with an adjustable shaft between them. Power looms may use temple cylinders. Pins can leave a series of holes in the selvages (these may be from stenter pins used in post-processing).

Handlooms to power looms

A power loom is a loom powered by a source of energy other than the weaver's muscles. When power looms were developed, other looms came to be referred to as handlooms. Most cloth is now woven on power looms, but some is still woven on handlooms.

The development of power looms was gradual. The capabilities of power looms gradually expanded, but handlooms remained the most cost-effective way to make some types of textiles for most of the 1800s. Many improvements in loom mechanisms were first applied to hand looms (like the dandy loom), and only later integrated into power looms.

Edmund Cartwright built and patented a power loom in 1785, and it was this that was adopted by the nascent cotton industry in England. The silk loom made by Jacques Vaucanson in 1745 operated on the same principles but was not developed further. The invention of the flying shuttle by John Kay allow a hand weaver to weave broadwoven cloth without an assistant, and was also critical to the development of a commercially successful power loom. Cartwright's loom was impractical but the ideas behind it were developed by numerous inventors in the Manchester area of England where, by 1818, there were 32 factories containing 5,732 looms.

The Horrocks loom was viable, but it was the Roberts Loom in 1830 that marked the turning point. Incremental changes to the three motions continued to be made. The problems of sizing, stop-motions, consistent take-up, and a temple to maintain the width remained. In 1841, Kenworthy and Bullough produced the Lancashire Loom which was self-acting or semi-automatic. This enables a youngster to run six looms at the same time. Thus, for simple calicos, the power loom became more economical to run than the handloom – with complex patterning that used a dobby or Jacquard head, jobs were still put out to handloom weavers until the 1870s. Incremental changes were made such as the Dickinson Loom, culminating in the Keighley-born inventor Northrop, who was working for the Draper Corporation in Hopedale producing the fully automatic Northrop Loom. This loom recharged the shuttle when the pirn was empty. The Draper E and X models became the leading products from 1909. They were challenged by synthetic fibres such as rayon.

By 1942, faster, more efficient, and shuttleless Sulzer and rapier looms had been introduced.

Symbolism and cultural significance
The loom is a symbol of cosmic creation and the structure upon which individual destiny is woven. This symbolism is encapsulated in the classical myth of Arachne who was changed into a spider by the goddess Athena, who was jealous of her skill at the godlike craft of weaving. In Maya civilization the goddess Ixchel taught the first woman how to weave at the beginning of time.

title: Loom


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Earth observation satellite

An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitoring, meteorology, cartography and others. The most common type are Earth imaging satellites, that take satellite images, analogous to aerial photographs; some EO satellites may perform remote sensing without forming pictures, such as in GNSS radio occultation.

The first occurrence of satellite remote sensing can be dated to the launch of the first artificial satellite, Sputnik 1, by the Soviet Union on October 4, 1957. Sputnik 1 sent back radio signals, which scientists used to study the ionosphere. The United States Army Ballistic Missile Agency launched the first American satellite, Explorer 1, for NASA's Jet Propulsion Laboratory on January 31, 1958. The information sent back from its radiation detector led to the discovery of the Earth's Van Allen radiation belts. The TIROS-1 spacecraft, launched on April 1, 1960, as part of NASA's Television Infrared Observation Satellite (TIROS) program, sent back the first television footage of weather patterns to be taken from space.

In 2008, more than 150 Earth observation satellites were in orbit, recording data with both passive and active sensors and acquiring more than 10 terabits of data daily. By 2021, that total had grown to over 950, with the largest number of satellites operated by US-based company Planet Labs.

Most Earth observation satellites carry instruments that should be operated at a relatively low altitude. Most orbit at altitudes above 500 to 600 km. Lower orbits have significant air-drag, which makes frequent orbit reboost maneuvers necessary. The Earth observation satellites ERS-1, ERS-2 and Envisat of European Space Agency as well as the MetOp spacecraft of EUMETSAT are all operated at altitudes of about 800 km. The Proba-1, Proba-2 and SMOS spacecraft of European Space Agency are observing the Earth from an altitude of about 700 km. The Earth observation satellites of UAE, DubaiSat-1 & DubaiSat-2 are also placed in Low Earth orbits (LEO) orbits and providing satellite imagery of various parts of the Earth.

To get global coverage with a low orbit, a polar orbit is used. A low orbit will have an orbital period of roughly 100 minutes and the Earth will rotate around its polar axis about 25° between successive orbits. The ground track moves towards the west 25° each orbit, allowing a different section of the globe to be scanned with each orbit. Most are in Sun-synchronous orbits.

A geostationary orbit, at 36000 km, allows a satellite to hover over a constant spot on the earth since the orbital period at this altitude is 24 hours. This allows uninterrupted coverage of more than 1/3 of the Earth per satellite, so three satellites, spaced 120° apart, can cover the whole Earth. This type of orbit is mainly used for meteorological satellites.

History
Herman Potočnik explored the idea of using orbiting spacecraft for detailed peaceful and military observation of the ground in his 1928 book, The Problem of Space Travel. He described how the special conditions of space could be useful for scientific experiments. The book described geostationary satellites (first put forward by Konstantin Tsiolkovsky) and discussed communication between them and the ground using radio, but fell short of the idea of using satellites for mass broadcasting and as telecommunications relays.

Weather

A weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth. These meteorological satellites, however, see more than clouds and cloud systems. City lights, fires, effects of pollution, auroras, sand and dust storms, snow cover, ice mapping, boundaries of ocean currents, energy flows, etc., are other types of environmental information collected using weather satellites.

Weather satellite images helped in monitoring the volcanic ash cloud from Mount St. Helens and activity from other volcanoes such as Mount Etna. Smoke from fires in the western United States such as Colorado and Utah have also been monitored.

Environmental monitoring

Other environmental satellites can assist environmental monitoring by detecting changes in the Earth's vegetation, atmospheric trace gas content, sea state, ocean color, and ice fields. By monitoring vegetation changes over time, droughts can be monitored by comparing the current vegetation state to its long term average. For example, the 2002 oil spill off the northwest coast of Spain was watched carefully by the European ENVISAT, which, though not a weather satellite, flies an instrument (ASAR) which can see changes in the sea surface. Anthropogenic emissions can be monitored by evaluating data of tropospheric NO2 and SO2.

These types of satellites are almost always in Sun-synchronous and "frozen" orbits. A Sun-synchronous orbit passes over each spot on the ground at the same time of day, so that observations from each pass can be more easily compared, since the Sun is in the same spot in each observation. A "frozen" orbit is the closest possible orbit to a circular orbit that is undisturbed by the oblateness of the Earth, gravitational attraction from the Sun and Moon, solar radiation pressure, and air drag.

Mapping
Terrain can be mapped from space with the use of satellites, such as Radarsat-1 and TerraSAR-X.

International regulations

According to the International Telecommunication Union (ITU), Earth exploration-satellite service (also: Earth exploration-satellite radiocommunication service) is – according to Article 1.51 of the ITU Radio Regulations (RR) – defined as: A radiocommunication service between earth stations and one or more space stations, which may include links between space stations, in which: This service may also include feeder links necessary for its operation.
 * information relating to the characteristics of the Earth and its natural phenomena, including data relating to the state of the environment, is obtained from passive or active sensors on satellites;
 * similar information is collected from airborne or Earth-based platforms;
 * such information may be distributed to earth stations within the system concerned;
 * platform interrogation may be included.

Classification
This radiocommunication service is classified in accordance with ITU Radio Regulations (article 1) as follows:

Fixed service (article 1.20)
 * Fixed-satellite service (article 1.21)
 * Inter-satellite service (article 1.22)
 * Earth exploration-satellite service
 * Meteorological-satellite service (article 1.52)

Frequency allocation
The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012).

In order to improve harmonisation in spectrum utilisation, the majority of service-allocations stipulated in this document were incorporated in national Tables of Frequency Allocations and Utilisations which is with-in the responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared. However, military usage, in bands where there is civil usage, will be in accordance with the ITU Radio Regulations.
 * primary allocation: is indicated by writing in capital letters (see example below)
 * secondary allocation: is indicated by small letters
 * exclusive or shared utilization: is within the responsibility of administrations

 * Example of frequency allocation:

title: Earth observation satellite


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Leiden

Leiden (in English and archaic Dutch also Leyden) is a city and municipality in the province of South Holland, Netherlands. The municipality of Leiden has a population of 127,046 (31 January 2023), but the city forms one densely connected agglomeration with its suburbs Oegstgeest, Leiderdorp, Voorschoten and Zoeterwoude with 215,602 inhabitants. The Netherlands Central Bureau of Statistics (CBS) further includes Katwijk in the agglomeration which makes the total population of the Leiden urban agglomeration 282,207 and in the larger Leiden urban area also Teylingen, Noordwijk, and Noordwijkerhout are included with in total 365,913 inhabitants. Leiden is located on the Oude Rijn, at a distance of some 20 km from The Hague to its south and some 40 km from Amsterdam to its north. The recreational area of the Kaag Lakes (Kagerplassen) lies just to the northeast of Leiden.

A university city since 1575, Leiden has been one of Europe's most prominent scientific centres for more than four centuries. Leiden is a typical university city, university buildings are scattered throughout the city and the many students from all over the world give the city a bustling, vivid and international atmosphere. Many important scientific discoveries have been made here, giving rise to Leiden's motto: 'City of Discoveries'. The city houses Leiden University, the oldest university of the Netherlands, and Leiden University Medical Center. Leiden University is one of Europe's top universities, with thirteen Nobel Prize winners. It is a member of the League of European Research Universities and positioned highly in all international academic rankings. It is twinned with Oxford, the location of the United Kingdom's oldest university. Leiden University and Leiden University of Applied Sciences (Leidse Hogeschool) together have around 35,000 students. Modern scientific medical research and teaching started in the early 18th century in Leiden with Boerhaave.

Leiden is a city with a rich cultural heritage, not only in science, but also in the arts. One of the world's most famous painters, Rembrandt, was born and educated in Leiden. Other Leiden painters include Lucas van Leyden, Jan van Goyen and Jan Steen.

History
Leiden was formed on an artificial hill (today called the Burcht van Leiden) at the confluence of the rivers Oude and Nieuwe Rijn (Old and New Rhine). The settlement was called Leithon. The name is from Germanic *leitha (canal).

Leiden has erroneously been associated with the Roman outpost Lugdunum Batavorum. This was thought to be located at the Burcht of Leiden, and the city's name was thought to be derived from the Latin name Lugdunum. However, the castellum was in fact closer to the town of Katwijk, whereas the Roman settlement near Leiden was called Matilo.

Siege of 1420
In 1420, during the Hook and Cod wars, Duke John III of Bavaria along with his army marched from Gouda in the direction of Leiden in order to conquer the city since Leiden did not pay the new Count of Holland Jacqueline, Countess of Hainaut, his niece and only daughter of Count William VI of Holland.

Burgrave Filips of Wassenaar and the other local noblemen of the Hook faction assumed that the duke would besiege Leiden first and send small units out to conquer the surrounding citadels. But John of Bavaria chose to attack the citadels first.

He rolled the cannons along with his army but one which was too heavy went by ship. By firing at the walls and gates with iron balls the citadels fell one by one. Within a week John of Bavaria conquered the castles of Poelgeest, Ter Does, Hoichmade, de Zijl, ter Waerd, Warmond and de Paddenpoel.

On 24 June the army appeared before the walls of Leiden. On 17 August 1420, after a two-month siege, the city surrendered to John of Bavaria. The burgrave Filips of Wassenaar was stripped of his offices and rights and lived out his last years in captivity.

16th to 18th centuries

Leiden flourished in the 16th and 17th century. At the close of the 15th century, the weaving establishments of Leiden (mainly broadcloth) were very important. In the same period, Leiden developed an important printing and publishing industry. Printers Lucas van Leyden and Otto van Veen lived here, and so did Christoffel Plantijn. One of Christoffel's pupils was Lodewijk Elzevir (1547–1617), who established the largest bookshop and printing works in Leiden, a business continued by his descendants through 1712.

In 1572, the city sided with the Dutch Revolt against Spanish rule and played an important role in the Eighty Years' War. It was besieged from May to October 1574 by the Spanish but was relieved by the cutting of the dikes, thus enabling ships to carry provisions to the inhabitants. William I of Orange founded the University of Leiden in 1575 as a reward for their heroic defense. The end of the siege is still celebrated in Leiden on October 3 each year. According to tradition, the citizens of Leiden were offered the choice between a university and a certain exemption from taxes and chose the university. The siege is notable also for being the first instance in Europe of the issuance of paper money, with paper taken from prayer books being stamped using coin dies when silver ran out.

Leiden is known as the place where the Pilgrims and some of the settlers of New Amsterdam  lived, operating a printing press for a time in the early 17th century before their departure to Massachusetts and New Amsterdam in the New World.

Leiden prospered in the 17th century, in part because of the impetus to the textile industry by refugees from Flanders. The city had lost about a third of its 15,000 citizens during the siege of 1574, but it quickly recovered to 45,000 in 1622 and may have come near to 70,000 c. 1670. During the Dutch Golden Era, Leiden was the second largest city of Holland after Amsterdam. It played a crucial role in the establishment of modern chemistry and medicine due to the work by Herman Boerhaave (1668–1738).

Leiden slumped from the late 17th century on, mainly due to the decline of the textile industries. The baize manufacture was given up at the beginning of the 19th century, although industry remained central to Leiden economy. This decline can be seen in the fall in population, which had sunk to 30,000 between 1796 and 1811, and in 1904 was 56,044.

Leiden was the publishing place from the 17th to the early 19th century of the important journal Nouvelles Extraordinaires de Divers Endroits, known also as Gazette de Leyde.

19th and 20th centuries
On 12 January 1807, a catastrophe struck the city when a boat loaded with 17400 kg of gunpowder blew up in the middle of Leiden. 151 people were killed, over 2,000 were injured and some 220 homes were destroyed. King Louis Bonaparte personally visited the city to provide assistance to the victims. Although located in the centre of the city, the area destroyed remained empty for many years. In 1886 the space was turned into a public park, the Van der Werff park.

In 1842, the railroad from Leiden to Haarlem was inaugurated and one year later the railway to The Hague (Den Haag) was completed, resulting in some social and economic improvement. Perhaps the most important piece of Dutch history contributed by Leiden was the Constitution of the Netherlands. Johan Rudolf Thorbecke (1798–1872) wrote the Dutch Constitution in April 1848 in his house at Garenmarkt 9 in Leiden.

Leiden's reputation as the "city of books" continued through the 19th century with the establishment of publishing dynasties by Evert Jan Brill and Albertus Willem Sijthoff. Sijthoff, who rose to prominence in the trade of translated books, wrote a letter in 1899 to Queen Wilhelmina regarding his opposition to becoming a signatory to the Berne Convention for the Protection of Literary and Artistic Works. He felt that international copyright restrictions would stifle the Dutch publishing industry.

Leiden began to expand beyond its 17th-century moats around 1896 and the number of citizens surpassed 50,000 in 1900. After 1920, new industries were established in the city, such as the canning and metal industries. During World War II, Leiden was hit hard by Allied bombardments. The areas surrounding the railway station and Marewijk were almost completely destroyed.

The University of Leiden is famous for its many discoveries including Snell's law (by Willebrord Snellius) and the famous Leyden jar, a capacitor made from a glass jar, invented in Leiden by Pieter van Musschenbroek in 1746. Another development was in cryogenics: Heike Kamerlingh Onnes (1913 Nobel prize winner in physics) liquefied helium for the first time (1908) and later managed to reach a temperature of less than one degree above the absolute minimum. Albert Einstein also spent some time at Leiden University during his early to middle career.

Leiden today
The city's biggest and most popular annual festival is celebrated on 3 October and is called simply 3 Oktober. The people of Leiden celebrate the end of the Spanish siege of 1574. It typically takes place over the course of two to three days and includes parades, a hutspot feast, historical reenactments, a funfair and other events. Since 2006, the city has also hosted the annual Leiden International Film Festival.

Leiden has important functions as a shopping and trade centre for communities around the city.

The city also houses the Eurotransplant, the international organization responsible for the mediation and allocation of organ donation procedures in Austria, Belgium, Croatia, Germany, Luxembourg, the Netherlands and Slovenia. Leiden also houses the headquarters of Airbus, a global pan-European aerospace and defence corporation and a leading defence and military contractor worldwide. The group includes Airbus, the leading manufacturer of commercial aircraft worldwide.

Rivers, canals and parks
The two branches of the Oude Rijn, which enter Leiden on the east, unite in the centre of the city. The city is further intersected by numerous small canals with tree-bordered quays. On the west side of the city, the Hortus Botanicus and other gardens extend along the old Singel, or outer canal. The Leidse Hout park, which contains a small deer park, lies on the northwest border with Oegstgeest. The Van der Werf Park is named after the mayor, who defended the city against the Spaniards in 1574. The city was beleaguered for months and many died from famine. The open space for the park was formed by the accidental explosion of a ship loaded with gunpowder in 1807, which destroyed hundreds of houses, including that of the Elsevier family of printers.

Buildings of interest
Because of the economic decline from the end of the 17th until the middle of the 19th century, much of the 16th- and 17th-century city centre is still intact. It is the second largest 17th-century town centre in the Netherlands, the largest being Amsterdam's city centre.

A hundred buildings in the centre are decorated with large murals of poetry, part of a wall poem project active from 1992, and still ongoing.

Fortifications
At the strategically important junction of the two arms of the Oude Rijn stands the old castle de Burcht, a circular tower built on an earthen mound. The mound probably was a refuge against high water before a small wooden fortress was built on top of it in the 11th century. The citadel is a so-called motte-and-bailey castle. Of Leiden's old city gates only two are left, the Zijlpoort and the Morspoort, both dating from the end of the 17th century. Apart from one small watch tower on the Singel nothing is left of the town's city walls. Another former fortification is the Gravensteen. Built as a fortress in the 13th century it has since served as house, library and prison. Presently it is one of the university's buildings.

Churches

The chief of Leiden's numerous churches are the Hooglandse Kerk (or the church of St Pancras, built in the 15th century and containing a monument to Pieter Adriaansz. van der Werff) and the Pieterskerk (church of St Peter (1315)) with monuments to Scaliger, Boerhaave and other famous scholars. From a historical perspective the Marekerk is interesting too. Arent van 's Gravesande designed that church in 1639. Other fine examples of his work in Leiden are in the Stedelijk Museum De Lakenhal (the municipal museum of fine arts), and the Bibliotheca Thysiana. The growing city needed another church and the Marekerk was the first Protestant church to be built in Leiden (and in Holland) after the Reformation. It is an example of Dutch Classicism. In the drawings by Van 's Gravesande the pulpit is the centrepiece of the church. The pulpit is modelled after the one in the Nieuwe Kerk at Haarlem (designed by Jacob van Campen). The building was first used in 1650, and is still in use. The Heilige Lodewijkkerk is first catholic church in Leiden that was built after the Reformation. This church was given to the Catholics after the gunpowder explosion in 1807, which killed 150 inhabitants and destroyed a large part of the city centre. The 'Waalse Kerk' (Breestraat 63) was originally part of the Katharina Hospital. In 1584 it became the church of Protestant refugees from the Southern Netherlands (Brugge) and France. Later churches in the centre include the St. Joseph in expressionistic style.

University buildings

The city centre contains many buildings that are in use by the University of Leiden. The Academy Building is housed in a former 16th-century convent. Among the institutions connected with the university are the national institution for East Indian languages, ethnology and geography; the botanical gardens, founded in 1587; the observatory (1860); the museum of antiquities (Rijksmuseum van Oudheden); and the ethnographical museum, of which P.F. von Siebold's Japanese collection was the nucleus (Rijksmuseum voor Volkenkunde). This collection is now housed in a separate museum called the SieboldHuis. The Bibliotheca Thysiana occupies an old Renaissance building of the year 1655. It is especially rich in legal works and vernacular chronicles. Noteworthy are also the many special collections at Leiden University Library among which those of the Society of Dutch Literature (1766) and the collection of casts and engravings. In recent years the university has built the Leiden Bio Science Park at the city's outskirts to accommodate the Science departments.

Other buildings

 * Stadhuis (City Hall), a 16th-century building that was badly damaged by a fire in 1929 but has its Renaissance façade designed by Lieven de Key still standing
 * Gemeenlandshuis van Rijnland (1596, restored in 1878)
 * De Waag (English: weigh house), built by Pieter Post
 * Gravensteen – a former 15th century jail at the Gerecht square (former court-house)
 * Stedelijk Gymnasium (aka Latijnse School) – the old gymnasium (1599)
 * Heilige Geest Weeshuis (a former Holy Spirit Orphanage) – a complex of 16th century buildings.
 * Molen de Valk – a corn-grinding windmill, now home to a museum (1743)
 * Pesthuis, which was built during 1657–1661 at that time just outside the city for curing patients suffering the bubonic plague. However, after it was built the feared disease did not occur in the Netherlands anymore so it was never used for its original purpose. The building has been used as a military hospital, prison, national asylum and army museum. Until 2019, it served as the entrance of Naturalis. This museum, one of the largest natural history museums in the world, was recently renovated and is a building of interest in itself.
 * Stadstimmerwerf – the city carpenter's yard or construction yard (1612), built by Lieven de Key (c. 1560–1627). The former residence of the city's master carpenter is open to the public and is in use as an art gallery of a local visual artists collective.

Museums

 * Rijksmuseum van Oudheden (National Museum of Antiquities)
 * Museum Volkenkunde (National Museum of Ethnology)
 * Naturalis Biodiversity Center
 * Rijksmuseum Boerhaave
 * Stedelijk Museum de Lakenhal
 * Japan Museum Sieboldhuis
 * Museum de Valk
 * Leiden American Pilgrim Museum
 * Corpus (in Oegstgeest, but almost directly next to the border with Leiden)
 * Hortus Botanicus Leiden
 * Museum Het Leids Weverhuis
 * Young Rembrandt Studio
 * Erfgoed Leiden en Omstreken
 * Anatomisch Museum Leiden

Public transport
Bus transport in Leiden is provided by Arriva.

Railway stations within the municipality of Leiden are:
 * Leiden Centraal
 * Leiden Lammenschans
 * De Vink

Notable people
The following is a selection of important Leidenaren throughout history:

Public officials and scholars

 * William II, Count of Holland (1228–1256) Count of Holland 1234-1256
 * Floris V, Count of Holland (1254–1296) Count of Holland and Zeeland 1256–1296
 * John of Leiden (1509–1536) leader of the Anabaptist Münster Rebellion
 * William Brewster (1568–1644) pilgrim, Mayflower passenger in 1620
 * Daniel Heinsius (1580–1655) famous scholar of the Dutch Renaissance
 * William Bradford (1590–1657) pilgrim, leader of the American Plymouth Colony in Massachusetts
 * Franciscus Junius (1591–1677) pioneer of Germanic philology
 * Isaac Elzevir (1596–1651) Dutch publisher and printer, co-founder of House of Elzevir
 * Love Brewster (1611–1650/1) pilgrim and founder of Bridgewater, Massachusetts
 * Isaac Vossius (1618–1689) scholar, manuscript collector and Canon at Windsor Castle
 * Nicolaas Heinsius the Elder (1620–1681) Dutch classical scholar and poet
 * Johann Bachstrom (1688–1742) writer, scientist and Lutheran theologian
 * Gottfried, Freiherr van Swieten (1733–1803) diplomat, friend and patron of several great composers
 * Jan Bake (1787–1864) Dutch philologist and critic
 * Reinhart Dozy (1820–1883) Dutch scholar of Arabic of Huguenot origin
 * Cornelis Tiele (1830–1902) Dutch theologian and scholar
 * J. P. B. de Josselin de Jong (1886–1964) museum curator, founding father of modern Dutch anthropology and structural anthropology
 * Hans de Koster (1914–1992) Dutch politician, diplomat and businessman
 * twins Alfred Kossmann (1922–1998) poet and prose writer & Ernst Kossmann (1922–2003) historian
 * Leendert Ginjaar (1928–2003) Dutch politician and chemist
 * Laurens Jan Brinkhorst (born 1937) retired Dutch politician and diplomat
 * Ankie Broekers-Knol (born 1946) Dutch politician, jurist and Minister
 * Carel Stolker (born 1954), rector magnificus and president of Leiden University from 2013 until 2021
 * Princess Laurentien of the Netherlands (born 1966) wife of Prince Constantijn
 * Kajsa Ollongren (born 1967) Dutch-Swedish politician, Deputy Prime Minister of the Netherlands
 * Julius Terpstra (born 1989) Dutch politician

The arts

 * Cornelis Engebrechtsz. (ca.1462–1527) early Dutch painter
 * Lucas van Leyden (1494–1533) Dutch painter and printmaker in engraving and woodcut
 * Jan van Goyen (1596–1656) Dutch landscape painter
 * Justus van Egmont (1601–1674) painter and tapestry designer
 * Rembrandt van Rijn (1606– 1669) Dutch draughtsman, painter and printmaker
 * Willem van de Velde the Elder (1610/11–1693) Dutch Golden Age seascape painter
 * Frans Post (1612–1680) Dutch Golden Age painter
 * Gerard Dou (1613–1675) Dutch Golden Age painter
 * Jan Steen (ca.1626–1679) Dutch Golden Age genre painter
 * Gabriel Metsu (1629–1667) painter of history paintings, still life, portraits and genre works
 * Willem van de Velde the Younger (1633-1707) Dutch marine painter
 * Frans van Mieris the Elder (1635–1681) Dutch Golden Age genre and portrait painter
 * Jan Gaykema Jacobsz. (1798–1875) Dutch painter, draughtsman and botanical illustrator
 * Jan Elias Kikkert (1843–1925) Dutch lithographer and watercolorist of street scenes of Leiden
 * Coenraad V. Bos (1875–1955) Dutch pianist, an accompanist to singers of lieder
 * Theo van Doesburg (1883–1931) Dutch artist, founder and leader of De Stijl
 * Ernst Winar (1894–1978) Dutch actor and film director
 * Nina Foch (1924–2008) Dutch American actress and drama teacher
 * Michel Waisvisz (1949–2008) Dutch composer, performer, inventor of experimental electronic musical instruments and artistic director of STEIM 1981-2008
 * Leoni Jansen (born 1955) TV personality and anchor-woman, singer and stage-director
 * Daniel Reuss (born 1961) Dutch conductor, primarily a choral conductor
 * Isa Hoes (born 1967) Dutch actress and voice actress
 * Eva Dorrepaal (born 1970) Dutch actress
 * Armin van Buuren (born 1976) Dutch DJ, record producer and remixer
 * Carice van Houten (born 1976) Dutch actress and singer
 * Dyro (born 1992) Dutch DJ and Electronic dance music producer

Science

 * Rembert Dodoens (1517–1585) botanist, died in Leiden
 * Charles de L'Écluse (1526–1609) botanist, horticulturist and director of Hortus Botanicus Leiden
 * Ludolph van Ceulen (1540–1610) mathematician, computed the number π, pi
 * Willebrord Snellius (1580–1626) Dutch astronomer and mathematician
 * Herman Boerhaave (1668–1738) botanist, chemist, Christian humanist and physician
 * Bernhard Siegfried Albinus (1697–1770) a German-born Dutch anatomist
 * Gerard van Swieten (1700–1772) Dutch physician, personal physician of Maria Theresa
 * Petrus Camper FRS (1722–1789) Dutch physician, anatomist, physiologist, midwife, zoologist, anthropologist, palaeontologist and a naturalist
 * Philipp Franz von Siebold (1796–1866) German physician and botanist, studied Japanese flora and fauna
 * Johannes Diderik van der Waals (1837–1923) Dutch theoretical physicist, winner of the 1910 Nobel prize in Physics
 * Hendrik Lorentz (1853–1928) Dutch physicist, joint winner of the 1902 Nobel Prize in Physics
 * Heike Kamerlingh Onnes (1853–1926) Dutch physicist and winner of the 1913 Nobel prize in Physics
 * Willem Einthoven (1860–1927) Dutch physician and physiologist
 * Pieter Zeeman (1865–1943) Dutch physicist, joint winner of the 1902 Nobel Prize in Physics
 * Willem de Sitter (1872–1934) Dutch mathematician, physicist and astronomer
 * Albert Einstein (1879–1955) lecturer/researcher at Leiden University, variously between 1916 and 1930
 * Paul Ehrenfest (1880–1933) Austrian/Dutch theoretical physicist, contributed to statistical mechanics
 * Geertruida de Haas-Lorentz (1885–1973) female Dutch physicist, worked on Brownian motion and electrical noise theory
 * Jan Oort (1900–1992) Dutch astronomer, pioneer in radio astronomy
 * Hendrik Casimir (1909–2000) Dutch physicist
 * Ewine van Dishoeck (born 1955) Dutch astronomer, chemist, molecular astrophysicist

Sport

 * Willem Slijkhuis (1923–2003) Dutch middle-distance runner, won two bronze medals in the 1948 Summer Olympics
 * Sandra Le Poole (born 1959) retired field hockey player, team gold medallist at the 1984 Summer Olympics
 * Ronald Florijn (born 1961) former rower, twice team gold medallist, at the 1988 and 1996 Summer Olympics
 * Carina Benninga (born 1962) & Taco van den Honert (born 1966) former Dutch field hockey players, team gold medallist at the 1984 Summer Olympics and team bronze medallist at the 1988 Summer Olympics
 * Alfons Groenendijk (born 1964) former footballer with 413 club caps and current manager
 * Gerritjan Eggenkamp (born 1975) Dutch rower, team silver medallist at the 2004 Summer Olympics
 * Rodney Glunder (born 1975) retired kickboxer, mixed martial artist, professional wrestler and boxer
 * Tim de Cler (born 1978) Dutch former footballer with 361 club caps
 * Erik van den Doel (born 1979) Dutch chess Grandmaster
 * Merel Witteveen (born 1985) sailor, team silver medallist at the 2008 Summer Olympics
 * Biurakn Hakhverdian (born 1985) & Iefke van Belkum (born 1986) Dutch water polo players, team gold medallist at the 2008 Summer Olympics
 * Gegard Mousasi (born 1985) Dutch mixed martial artist and former kickboxer
 * Laurine van Riessen (born 1987) long track speed skater and track cyclist, bronze medallist at the 2010 Winter Olympics
 * Kjeld Nuis (born 1989) Dutch speed skater, world record holder and gold medallist at the 2018 Winter Olympics over 1000 metre and 1500 metre
 * Chantal de Ridder (born 1989) Dutch football striker, 46 caps with the Netherlands women's national football team
 * Esmee Visser (born 1996) long-distance speed skater, gold medallist in the 2018 Winter Olympics in the women's 5000 metres

Others

 * Maria Swanenburg (1839–1915) Dutch serial killer, murdered at least 27 people and suspected of killing more than 90
 * Aemilianus van Heel (1907–1938) Franciscan friar who served as a missionary in China
 * Marinus van der Lubbe (1909–1934) executed for the Reichstag fire in Berlin in 1933
 * Buurtpoes Bledder (2011–2013) male domestic cat, media star for his exploits in the city
 * Kirtie Ramdas (born 1980), Dutch television presenter and actress

Twin cities – sister cities
Leiden is twinned with:

Miscellaneous
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 * The coat of arms of Leiden is two red keys, crossed in an X-shape on a white background. These keys are the Keys of Heaven held by St. Peter, for whom a large church in the city centre is named. Because of this coat of arms, Leiden is referred to as the "Sleutelstad" ("the key city").
 * For a time Leiden held the title "The Coldest Place on Earth" because of the developments in cryogenics in a laboratory there. Heike Kamerlingh Onnes (1913 Nobel prize winner in physics) liquefied helium for the first time (1908), and later managed to reach a temperature of less than one degree above Absolute zero.
 * The Norwegian cheese "nøkkelost" ("key cheese") is named after the keys in coat of arms of Leyden, as it is a variation of Leyden cheese.
 * The following places and things are named after this city:
 * Leyden, New York, USA
 * Leyden, Massachusetts, USA
 * Leyden Township, Cook County, Illinois, USA
 * Leiden scale, for measuring extreme low temperatures.
 * Factor V Leiden is named after the city of Leiden where it was discovered in 1994.
 * The Leyden jar, a capacitor made from a glass jar, was invented here by Pieter van Musschenbroek in 1746. It was actually first invented by Ewald Georg von Kleist the year before, but the name "Leyden jar" stuck.
 * Leiden's Stadhuis (Town Hall) has a poem in the form of a cryptogram on its façade that records the date 1574 in Roman numerals, the year of the "Black Famine" or Spanish siege (W equals two Vs):

(Dutch: "When the Black Famine had brought to the death nearly six thousand persons, then God the Lord repented, and gave bread again as much as we could wish".)

Sports
Zorg en Zekerheid Leiden is the basketball club of Leiden. In 2011, 2013 and 2021 they won the National Title, in 2010 and 2012 the National Cup and in 2011 and 2012 the National Super Cup. The club also played in the FIBA EuroChallenge and reached the Second Round (Best 16) in 2011/2012.

title: Leiden