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A rope is a group of yarns, plies, fibres, or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than similarly constructed cord, string, and twine.

Construction

Rope may be constructed of any long, stringy, fibrous material (e.g., rattan, a natural material), but generally is constructed of certain natural or synthetic fibres.^[1][2][3] Synthetic fibre ropes are significantly stronger than their natural fibre counterparts, they have a higher tensile strength, they are more resistant to rotting than ropes created from natural fibres, and they can be made to float on water.^[4] But synthetic ropes also possess certain disadvantages, including slipperiness, and some can be damaged more easily by UV light.^[5]

Common natural fibres for rope are Manila hemp, hemp, linen, cotton, coir, jute, straw, and sisal. Synthetic fibres in use for rope-making include polypropylene, nylon, polyesters (e.g. PET, LCP, Vectran), polyethylene (e.g. Dyneema and Spectra), Aramids (e.g. Twaron, Technora and Kevlar) and acrylics (e.g. Dralon). Some ropes are constructed of mixtures of several fibres or use co-polymer fibres. Wire rope is made of steel or other metal alloys. Ropes have been constructed of other fibrous materials such as silk, wool, and hair, but such ropes are not generally available. Rayon is a regenerated fibre used to make decorative rope.

The twist of the strands in a twisted or braided rope serves not only to keep a rope together, but enables the rope to more evenly distribute tension among the individual strands. Without any twist in the rope, the shortest strand(s) would always be supporting a much higher proportion of the total load.

• Construction
• Three-strand natural fibre laid line
• Construction of cable
• Hawser-laid rope (Seaman’s Pocket-Book, 1943)

Size measurement

Because rope has a long history, many systems have been used to specify the size of a rope. In systems that use the inch (Imperial and US customary measurement systems), large ropes over 1 inch (25.4 mm) diameter – such as those used on ships – are measured by their circumference in inches; smaller ropes have a nominal diameter based on the circumference divided by three (as a rough approximation of pi). In the metric system of measurement, the nominal diameter is given in millimetres. The current preferred international standard for rope sizes is to give the mass per unit length, in kilograms per metre. However, even sources otherwise using metric units may still give a “rope number” for large ropes, which is the circumference in inches.^[6]

Use

Rope has been used since prehistoric times.^[7] It is of paramount importance in fields as diverse as construction, seafaring, exploration, sports, theatre, and communications. Many types of knots have been developed to fasten with rope, join ropes, and utilize rope to generate mechanical advantage. Pulleys can redirect the pulling force of a rope in another direction, multiply its lifting or pulling power, and distribute a load over multiple parts of the same rope to increase safety and decrease wear.

Winches and capstans are machines designed to pull ropes.

Knotted ropes have historically been used for measurement and mathematics. For example, Ancient Egyptian rope stretchers used knotted ropes to measure distances, Middle Age European shipbuilders and architects performed calculations using arithmetic ropes, and some pre-colonial South American cultures used quipu for numerical record-keeping.

History

The use of ropes for hunting, pulling, fastening, attaching, carrying, lifting, and climbing dates back to prehistoric times. It is likely that the earliest “ropes” were naturally occurring lengths of plant fibre, such as vines, followed soon by the first attempts at twisting and braiding these strands together to form the first proper ropes in the modern sense of the word. The earliest evidence of suspected rope is a very small fragment of three-ply cord from a Neanderthal site dated 50,000 years ago.^[8][9] This item was so small, it was only discovered and described with the help of a high power microscope. It is slightly thicker than the average thumb-nail, and would not stretch from edge-to-edge across a little finger-nail. There are other ways fibres can twist in nature, without deliberate construction.^[10]

A tool dated between 35,000 and 40,000 years found in the Hohle Fels cave in south-western Germany has been identified as a means for making rope.^[11] It is a 20 cm (8 in) strip of mammoth ivory with four holes drilled through it. Each hole is lined with precisely cut spiral incisions. The grooves on three of the holes spiral in a clockwise direction from each side of the strip. The grooves on one hole spiral clockwise on one side, but counter-clockwise from the other side.^[12] Plant fibres have been found on it that could have come from when they fed through the holes and the tool twisted, creating a single ply yarn. Fiber-making experiments with a replica found that the perforations served as effective guides for raw fibers, making it easier to make a strong, elastic rope than simply twisting fibers by hand spiral incisions would have tended to keep the fibres in place.^[11][13] But the incisions cannot impart any twist to the fibres pulled through the holes.^[14] Other 15,000-year-old objects with holes with spiral incisions, made from reindeer antler, found across Europe are thought to have been used to manipulate ropes, or perhaps some other purpose.^[15] They were originally named “batons“, and thought possibly to have been carried as badges of rank.^[13][16]

Impressions of cordage found on fired clay provide evidence of string and rope-making technology in Europe dating back 28,000 years.^[17] Fossilized fragments of “probably two-ply laid rope of about 7 mm [0.28 in] diameter” were found in one of the caves at Lascaux, dating to approximately 15,000 BC.^[18]

The ancient Egyptians were probably the first civilization to develop special tools to make rope. Egyptian rope dates back to 4000 to 3500 BC and was generally made of water reed fibres.^[19] Other rope in antiquity was made from the fibres of date palms, flax, grass, papyrus, leather, or animal hair. The use of such ropes pulled by thousands of workers allowed the Egyptians to move the heavy stones required to build their monuments. Starting from approximately 2800 BC, rope made of hemp fibres was in use in China. Rope and the craft of rope making spread throughout Asia, India, and Europe over the next several thousand years.

From the Middle Ages until the 18th century, in Europe ropes were constructed in ropewalks, very long buildings where strands the full length of the rope were spread out and then laid up or twisted together to form the rope. The cable length was thus set by the length of the available rope walk. This is related to the unit of length termed cable length. This allowed for long ropes of up to 300 yards (270 m) long or longer to be made. These long ropes were necessary in shipping as short ropes would require splicing to make them long enough to use for sheets and halyards. The strongest form of splicing is the short splice, which doubles the cross-sectional area of the rope at the area of the splice, which would cause problems in running the line through pulleys. Any splices narrow enough to maintain smooth running would be less able to support the required weight.^{[citation needed]} Rope intended for naval use would have a coloured yarn, known as the “rogue’s yarn”, included in the layup. This enabled the source to be identified and to detect pilfering.^[20]

Leonardo da Vinci drew sketches of a concept for a ropemaking machine, but it was never built. Remarkable feats of construction were accomplished using rope but without advanced technology: In 1586, Domenico Fontana erected the 327 ton obelisk on Rome’s Saint Peter’s Square with a concerted effort of 900 men, 75 horses, and countless pulleys and meters of rope. By the late 18th century several working machines had been built and patented.

Some rope is still made from natural fibres, such as coir and sisal, despite the dominance of synthetic fibres such as nylon and polypropylene, which have become increasingly popular since the 1950s.

Nylon was discovered in the late 1930s and was first introduced into fiber ropes during World War II. Indeed, the first synthetic fiber ropes were small braided parachute cords and three-strand tow ropes for gliders, made of nylon during World War II.^[21]

Gallery

• History
• Ancient Egyptians were the first to document tools for ropemaking
• A ropemaker at work, c. 1425
• A German ropemaker, c. 1470
• Public demonstration of historical ropemaking technique
• A piece of preserved rope found on board the 16th century carrack Mary Rose
• A ropewalk in Karlskrona, Sweden
• Rope laying machines in a Scottish rope factory, November 1918
• Stanchions and velvet rope

Styles of rope

Laid or twisted rope

Laid rope, also called twisted rope, is historically the prevalent form of rope, at least in modern Western history. Common twisted rope generally consists of three strands and is normally right-laid, or given a final right-handed twist. The ISO 2 standard uses the uppercase letters S and Z to indicate the two possible directions of twist, as suggested by the direction of slant of the central portions of these two letters. The handedness of the twist is the direction of the twists as they progress away from an observer. Thus Z-twist rope is said to be right-handed, and S-twist to be left-handed.

Twisted ropes are built up in three steps. First, fibres are gathered and spun into yarns. A number of these yarns are then formed into strands by twisting. The strands are then twisted together to lay the rope. The twist of the yarn is opposite to that of the strand, and that in turn is opposite to that of the rope. It is this counter-twist, introduced with each successive operation, which holds the final rope together as a stable, unified object.^[22]

Traditionally, a three strand laid rope is called a plain- or hawser-laid, a four strand rope is called shroud-laid, and a larger rope formed by counter-twisting three or more multi-strand ropes together is called cable-laid.^[23] Cable-laid rope is sometimes clamped to maintain a tight counter-twist rendering the resulting cable virtually waterproof. Without this feature, deep water sailing (before the advent of steel chains and other lines) was largely impossible, as any appreciable length of rope for anchoring or ship to ship transfers, would become too waterlogged – and therefore too heavy – to lift, even with the aid of a capstan or windlass.

One property of laid rope is partial untwisting when used.^[24] This can cause spinning of suspended loads, or stretching, kinking, or hockling of the rope itself. An additional drawback of twisted construction is that every fibre is exposed to abrasion numerous times along the length of the rope. This means that the rope can degrade to numerous inch-long fibre fragments, which is not easily detected visually.^{[citation needed]}

Twisted ropes have a preferred direction for coiling. Normal right-laid rope should be coiled clockwise, to prevent kinking. Coiling this way imparts a twist to the rope. Rope of this type must be bound at its ends by some means to prevent untwisting.

Braided rope

While rope may be made from three or more strands,^[25] modern braided rope consists of a braided (tubular) jacket over strands of fibre (these may also be braided). Some forms of braided rope with untwisted cores have a particular advantage; they do not impart an additional twisting force when they are stressed. The lack of added twisting forces is an advantage when a load is freely suspended, as when a rope is used for rappelling or to suspend an arborist. Other specialized cores reduce the shock from arresting a fall when used as a part of a personal or group safety system.

Braided ropes are generally made from nylon, polyester, polypropylene or high performance fibres such as high modulus polyethylene (HMPE) and aramid. Nylon is chosen for its strength and elastic stretch properties. However, nylon absorbs water and is 10–15% weaker when wet. Polyester is about 90% as strong as nylon but stretches less under load and is not affected by water. It has somewhat better UV resistance, and is more abrasion resistant. Polypropylene is preferred for low cost and light weight (it floats on water) but it has limited resistance to ultraviolet light, is susceptible to friction and has a poor heat resistance.^{[citation needed]}

Braided ropes (and objects like garden hoses, fibre optic or coaxial cables, etc.) that have no lay (or inherent twist) uncoil better if each alternate loop is twisted in the opposite direction, such as in figure-eight coils, where the twist reverses regularly and essentially cancels out.

Single braid consists of an even number of strands, eight or twelve being typical, braided into a circular pattern with half of the strands going clockwise and the other half going anticlockwise. The strands can interlock with either twill or panama (Basked) or seldom plain weave. Kyosev introduced the German notation in English, where the floating length (German: Flechtigkeit) and the number of yarns in a group (German: Fädigkeit) in more natural way for braiding process are used, instead of the pattern names in weaving.^[25] The central void may be large or small; in the former case the term hollow braid is sometimes preferred.

Double braid, also called braid on braid, consists of an inner braid filling the central void in an outer braid, that may be of the same or different material. Often the inner braid fibre is chosen for strength while the outer braid fibre is chosen for abrasion resistance.

In a solid braid, (square braid, gasket, or form braid^[26] there are at least three or more groups of yarns, interlacing in complex (interlocking) structure. This construction is popular for gaskets and general purpose utility rope but rare in specialized high performance line.

Kernmantle rope has a core (kern) of long twisted fibres in the center, with a braided outer sheath or mantle of woven fibres. The kern provides most of the strength (about 70%), while the mantle protects the kern and determines the handling properties of the rope (how easy it is to hold, to tie knots in, and so on). In dynamic climbing line, core fibres are usually twisted to make the rope more elastic. Static kernmantle ropes are made with untwisted core fibres and tighter braid, which causes them to be stiffer in addition to limiting the stretch.

Other types

Plaited rope is made by braiding twisted strands, and is also called square braid.^[27] It is not as round as twisted rope and coarser to the touch. It is less prone to kinking than twisted rope and, depending on the material, very flexible and therefore easy to handle and knot. This construction exposes all fibres as well, with the same drawbacks as described above. Brait rope is a combination of braided and plaited, a non-rotating alternative to laid three-strand ropes. Due to its excellent energy-absorption characteristics, it is often used by arborists. It is also a popular rope for anchoring and can be used as mooring warps. This type of construction was pioneered by Yale Cordage.

Endless winding rope is made by winding single strands of high-performance yarns around two end terminations until the desired break strength or stiffness has been reached. This type of rope (often specified as cable to make the difference between a braided or twined construction) has the advantage of having no construction stretch as is the case with above constructions. Endless winding is pioneered by SmartRigging and FibreMax.

Rock climbing

The sport of rock climbing uses what is termed “dynamic” rope, an elastic rope which stretches under load to absorb the energy generated in arresting a fall without creating forces high enough to injure the climber. Such ropes are of kernmantle construction, as described below.

Conversely, “static” ropes have minimal stretch and are not designed to arrest free falls. They are used in caving, rappelling, rescue applications, and industries such as window washing.

The UIAA, in concert with the CEN, sets climbing-rope standards and oversees testing. Any rope bearing a GUIANA or CE certification tag is suitable for climbing. Climbing ropes cut easily when under load. Keeping them away from sharp rock edges is imperative. Previous falls arrested by a rope, damage to its sheath, and contamination by dirt or solvents all weaken a rope and can render it unsuitable for further sport use.

Rock climbing ropes are designated as suitable for single, double or twin use. A single rope is the most common, and is intended to be used by itself. These range in thickness from roughly 9 to 11 mm (0.35 to 0.43 in). Smaller diameter ropes are lighter, but wear out faster.

Double ropes are thinner than single, usually 9 mm (0.35 in) and under, and are intended for use in pairs. These offer a greater margin of safety against cutting, since it is unlikely that both ropes will be cut, but complicate both belaying and leading. Double ropes may be clipped into alternating pieces of protection, allowing each to stay straighter and reduce both individual and total rope drag.

Twin ropes are thin ropes which must be clipped into the same piece of protection, in effect being treated as a single strand. This adds security in situations where a rope may get cut. However new lighter-weight ropes with greater safety have virtually replaced this type of rope.^{[citation needed]}

The butterfly and alpine coils are methods of coiling a rope for carrying.

Gallery of μCT/micro-CT images and animations

2D images / sections

• Sections

2D flight-throughs/sections

• Sections
• Duration: 13 seconds.0:13
• Duration: 10 seconds.0:10
• Duration: 31 seconds.0:31
• Duration: 30 seconds.0:30

3D renderings

• Sections

3D flight-throughs/sections

• Sections

Handling

Rope made from hemp, cotton or nylon is generally stored in a cool dry place for proper storage. To prevent kinking it is usually coiled. To prevent fraying or unravelling, the ends of a rope are bound with twine (whipping), tape, or heat shrink tubing. The ends of plastic fibre ropes are often melted and fused solid; however, the rope and knotting expert Geoffrey Budworth warns against this practice thus:^[28]

Sealing rope ends this way is lazy and dangerous. A tugboat operator once sliced the palm of his hand open down to the sinews after the hardened (and obviously sharp) end of a rope that had been heat-sealed pulled through his grasp. There is no substitute for a properly made whipping.

If a load-bearing rope gets a sharp or sudden jolt or the rope shows signs of deteriorating, it is recommended that the rope be replaced immediately and should be discarded or only used for non-load-bearing tasks.^[29][30]

The average rope life-span is 5 years. Serious inspection should be given to line after that point.^{[citation needed]} However, the use to which a rope is put affects frequency of inspection. Rope used in mission-critical applications, such as mooring lines or running rigging, should be regularly inspected on a much shorter timescale than this, and rope used in life-critical applications such as mountain climbing should be inspected on a far more frequent basis, up to and including before each use.

Avoid stepping on climbing rope, as this might force tiny pieces of rock through the sheath, which can eventually deteriorate the core of the rope.

Ropes may be flemished into coils on deck for safety, presentation, and tidiness.

Many types of filaments in ropes are weakened by corrosive liquids, solvents, and high temperatures. Such damage is particularly treacherous because it is often invisible to the eye.^[31]

Shock loading should be avoided with general use ropes, as it can damage them.^[32] All ropes should be used within a safe working load, which is much less than their breaking strength.

A rope under tension – particularly if it has a great deal of elasticity – can be dangerous if parted. Care should be taken around lines under load.

Terminology

“Rope” is a material, and a tool. When it is assigned a specific function it is often referred to as a “line”, especially in nautical usage. A line may get a further distinction, for example sail control lines are known as “sheets” (e.g. A jib sheet).

A halyard is a line used to raise and lower a sail, typically with a shackle on its sail end. Other maritime examples of “lines” include anchor line, mooring line, fishing line, marline. Common items include clothesline and a chalk line.

In some marine uses the term rope is retained, such as man rope, bolt rope, and bell rope.

Maple syrup is a sweet syrup made from the sap of maple trees. In cold climates, these trees store starch in their trunks and roots before winter; the starch is then converted to sugar that rises in the sap in late winter and early spring. Maple trees are tapped by drilling holes into their trunks and collecting the sap, which is processed by heating to evaporate much of the water, leaving the concentrated syrup.

Maple syrup was first made by the Indigenous peoples of Northeastern North America. The practice was adopted by European settlers, who gradually changed production methods. Technological improvements in the 1970s further refined syrup processing. Almost all of the world’s maple syrup is produced in Canada and the United States.

Maple syrup is graded based on its colour and taste. Sucrose is the most prevalent sugar in maple syrup. In Canada, syrups must be made exclusively from maple sap to qualify as maple syrup and must also be at least 66 per cent sugar.^[1] In the United States, a syrup must be made almost entirely from maple sap to be labelled as “maple”, though states such as Vermont and New York have more restrictive definitions.

Maple syrup is often used as a condiment for pancakes, waffles, French toast, oatmeal, or porridge. It is also used as an ingredient in baking and as a sweetener or flavouring agent.^[2]

Sources

[edit]

Three species of maple (Acer) trees are predominantly used to produce maple syrup: the sugar maple (Acer saccharum),^[3][4] the black maple (A. nigrum),^[3][5] and the red maple (A. rubrum),^[3][6] because of the high sugar content (roughly two to five per cent) in the sap of these species.^[7] The black maple is included as a subspecies or variety in a more broadly viewed concept of A. saccharum, the sugar maple, by some botanists.^[8] Of these, the red maple has a shorter season because it buds earlier than sugar and black maples, which alters the flavour of the sap.^[9]

A few other species of maple are also sometimes used as sources of sap for producing maple syrup, including the box elder or Manitoba maple (Acer negundo),^[3][10] the silver maple (A. saccharinum),^[3][11] and the bigleaf maple (A. macrophyllum).^[12] In the Southeastern United States, Florida sugar maple (Acer floridanum) is occasionally used for maple syrup production.^[13]

Similar syrups may also be produced from walnut, birch, or palm trees, among other sources.^[14][15][16]

History

[edit]

Indigenous peoples

[edit]

Indigenous peoples living in northeastern North America were the first groups known to have produced maple syrup and maple sugar. According to Indigenous oral traditions, as well as archaeological evidence, maple tree sap was being processed into syrup long before Europeans arrived in the region.^[17][18] There are no authenticated accounts of how maple syrup production and consumption began,^[19] but various legends exist; one of the most popular involves maple sap being used in place of water to cook venison served to a chief.^[18] Indigenous tribes developed rituals around syrup-making, celebrating the Sugar Moon (the first full moon of spring) with a Maple Dance.^[20] Many aboriginal dishes replaced the salt traditional in European cuisine with maple syrup.^[18]

The Algonquians recognized maple sap as a source of energy and nutrition. At the beginning of the spring thaw, they made V-shaped incisions in tree trunks; they then inserted reeds or concave pieces of bark to run the sap into clay buckets or tightly woven birch-bark baskets. The maple sap was concentrated first by leaving it exposed to the cold temperatures overnight and disposing of the layer of ice that formed on top. Following that, the sap was transported by sled to large fires where it was boiled in clay pots to produce maple syrup. Often, multiple pots were used in conjunction, with the liquid being transferred between them as it grew more concentrated. Contrary to popular belief, syrup was not typically produced by dropping heated stones into wooden bowls, especially in northeast North America where Indigenous cultures had been using clay pots for thousands of years.^[21][19] However, modern and historic sources contain evidence that hot stones may have occasionally been used in the upper Midwest and Canada, where hollowed out logs and birchbark containers typically replaced clay pots.^[22]

European colonists

[edit]

In the early stages of European colonization in northeastern North America, local Indigenous peoples showed the arriving colonists how to tap the trunks of certain types of maples during the spring thaw to harvest the sap.^[23] André Thevet, the “Royal Cosmographer of France”, wrote about Jacques Cartier drinking maple sap during his Canadian voyages.^[24] By 1680, European settlers and fur traders were involved in harvesting maple products.^[25] However, rather than making incisions in the bark, the Europeans used the method of drilling tapholes in the trunks with augers. Prior to the 19th century, processed maple sap was used primarily as a source of concentrated sugar, in both liquid and crystallized-solid form, as cane sugar had to be imported from the West Indies.^[19][20]

Maple sugaring parties typically began to operate at the start of the spring thaw in regions of woodland with sufficiently large numbers of maples.^[23] Syrup makers first bored holes in the trunks, usually more than one hole per large tree; they then inserted wooden spouts into the holes and hung a wooden bucket from the protruding end of each spout to collect the sap. The buckets were commonly made by cutting cylindrical segments from a large tree trunk and then hollowing out each segment’s core from one end of the cylinder, creating a seamless, watertight container.^[19] Sap filled the buckets, and was then either transferred to larger holding vessels (barrels, large pots, or hollowed-out wooden logs), often mounted on sledges or wagons pulled by draft animals, or carried in buckets or other convenient containers.^[26] The sap-collection buckets were returned to the spouts mounted on the trees, and the process was repeated for as long as the flow of sap remained “sweet”. The specific weather conditions of the thaw period were, and still are, critical in determining the length of the sugaring season.^[27] As the weather continues to warm, a maple tree’s normal early spring biological process eventually alters the taste of the sap, making it unpalatable, perhaps due to an increase in amino acids.^[28]

The boiling process was very time-consuming. The harvested sap was transported back to the party’s base camp, where it was then poured into large vessels (usually made from metal) and boiled down to achieve the desired concentration.^[19] The sap was usually transported using large barrels pulled by horses or oxen to a central collection point, where it was processed either over a fire built out in the open or inside a shelter built for that purpose (the “sugar shack”).^[19][29]

Since 1850

[edit]

Around the time of the American Civil War (1861–1865), syrup makers started using large, flat sheet metal pans as they were more efficient for boiling than heavy, rounded iron kettles, because of a greater surface area for evaporation.^[29] Around this time, cane sugar replaced maple sugar as the dominant sweetener in the US; as a result, producers focused marketing efforts on maple syrup. The first evaporator, used to heat and concentrate sap, was patented in 1858. In 1872, an evaporator was developed that featured two pans and a metal arch or firebox, which greatly decreased boiling time.^[19] Around 1900, producers bent the tin that formed the bottom of a pan into a series of flues, which increased the heated surface area of the pan and again decreased boiling time. Some producers also added a finishing pan, a separate batch evaporator, as a final stage in the evaporation process.^[29]

Buckets began to be replaced with plastic bags, which allowed people to see at a distance how much sap had been collected. Syrup producers also began using tractors to haul vats of sap from the trees being tapped (the sugar bush) to the evaporator. Some producers adopted motor-powered tappers and metal tubing systems to convey sap from the tree to a central collection container, but these techniques were not widely used.^[19] Heating methods also diversified: modern producers use wood, oil, natural gas, propane, or steam to evaporate sap.^[29] Modern filtration methods were perfected to prevent contamination of the syrup.^[30]

A large number of technological changes took place during the 1970s. Plastic tubing systems that had been experimental since the early part of the century were perfected, and the sap came directly from the tree to the evaporator house.^[31] Vacuum pumps were added to the tubing systems, and preheaters were developed to recycle heat lost in the steam. Producers developed reverse-osmosis machines to take a portion of water out of the sap before it was boiled, increasing processing efficiency.^[19]

Improvements in tubing and vacuum pumps, new filtering techniques, “supercharged” preheaters, and better storage containers have since been developed. Research continues on pest control and improved woodlot management.^[19] In 2009, researchers at the University of Vermont unveiled a new type of tap that prevents backflow of sap into the tree, reducing bacterial contamination and preventing the tree from attempting to heal the bore hole.^[32] Experiments show that it may be possible to use saplings in a plantation instead of mature trees, dramatically boosting productivity per acre.^[33] As a result of the smaller tree diameter, milder diurnal temperature swings are needed for the tree to freeze and thaw, which enables sap production in milder climatic conditions outside of northeastern North America.^[34]

Processing

[edit]

Open pan evaporation methods have been streamlined since colonial days, but remain basically unchanged. Sap must first be collected and boiled down to obtain syrup. Maple syrup is made by boiling between 20 and 50 volumes of sap (depending on its concentration) over an open fire until 1 volume of syrup is obtained, usually at a temperature 4.1 °C (7.4 °F) over the boiling point of water. As the boiling point of water varies with changes in air pressure, the correct value for pure water is determined at the place where the syrup is being produced each time evaporation is begun and periodically throughout the day.^[29][35] Syrup can be boiled entirely over one heat source or can be drawn off into smaller batches and boiled at a more controlled temperature.^[36] Defoamers are often added during boiling.^[37]

Boiling the syrup is a tightly controlled process, which ensures appropriate sugar content. Syrup boiled too long will eventually crystallize, whereas under-boiled syrup will be watery, and will quickly spoil. The finished syrup has a density of 66° on the Brix scale (a hydrometric scale used to measure sugar solutions).^[38] The syrup is then filtered to remove precipitated “sugar sand”, crystals made up largely of sugar and calcium malate.^[39] These crystals are not toxic, but create a “gritty” texture in the syrup if not filtered out.^[40]

In addition to open pan evaporation methods, many large producers use the more fuel efficient reverse osmosis procedure to separate the water from the sap.^[41] Smaller producers can also use batchwise recirculating reverse osmosis, with the most energy-efficient operation taking the sugar concentration to 25% prior to boiling.^[42]

The higher the sugar content of the sap, the smaller the volume of sap is needed to obtain the same amount of syrup. To yield 1 unit of syrup, sap at 1.5 per cent sugar content will require 57 units, while sap at 3.5 per cent sugar content only needs 25 units of sap.^[43] The sap’s sugar content is highly variable and will fluctuate even within the same tree.^[44]

The filtered syrup is graded and packaged while still hot, usually at a temperature of 82 °C (180 °F) or greater. The containers are turned over after being sealed to sterilize the cap with the hot syrup. Packages can be made of metal, glass, or coated plastic, depending on volume and target market.^[45] The syrup can also be heated longer and further processed to create a variety of other maple products, including maple sugar, maple butter or cream, and maple candy or taffy.^[46]Duration: 11 seconds.0:11Maple sap harvesting

Off-flavours

[edit]

Off-flavours can sometimes develop during the production of maple syrup, resulting from contaminants in the boiling apparatus (such as disinfectants), microorganisms, fermentation products, metallic can flavours, and “buddy sap”, an off-flavour occurring late in the syrup season when tree budding has begun.^[47][48] In some circumstances, it is possible to remove off-flavours through processing.^[47][49]

Production

[edit]

Maple syrup production is centred in northeastern North America; however, given the correct weather conditions, it can be made wherever suitable species of maple trees grow, such as New Zealand, where there are efforts to establish commercial production.^[50] Climate change is dramatically impacting the production of maple syrup.^[51][52][53]

A maple syrup production farm is called a “sugarbush“. Sap is often boiled in a “sugar house” (also known as a “sugar shack”, “sugar cabin”, “sugar shanty”, or cabane à sucre), a building louvred at the top to vent the steam from the boiling sap.^{[54][55][56][57]}

Maples are usually tapped beginning at 30 to 40 years of age. Each tree can support between one and three taps, depending on its trunk diameter. The average maple tree will produce 35 to 50 litres (9.2 to 13.2 US gal) of sap per season, up to 12 litres (3.2 US gal) per day.^[58] This is roughly equal to seven per cent of its total sap. Tap seasons typically happen during late winter and spring and usually last for four to eight weeks, though the exact dates depend on the weather, location, and climate.^[59][60] The timing of the season and the region of maximum sap flow are both expected to be significantly altered by climate change by 2100.^[61]

During the day, sucrose stored in the roots for the winter rises through the trunk as sugary sap. A hole is bored into the trunk of the tree to allow the sap to flow out of a spile that is tapped in the hole.^[27] The taps are left in place for the season, and the sap flows during the day when the temperature is above freezing.^[62] Some producers also tap in autumn, though this practice is less common than spring tapping. Maples can continue to be tapped for sap until they are over 100 years old.^[58]

Commerce

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Until the 1930s, the United States produced most of the world’s maple syrup.^[63] Today, after rapid growth in the 1990s, Canada produces more than 80 per cent of the world’s maple syrup, producing about 73 million kg (80,000 short tons) in 2016.^[64] Within Canada, Quebec is the largest producer, responsible for 72 per cent of the world’s output; Canadian exports of maple syrup in 2016 were C$487 million (about US$360 million), with Quebec accounting for some 90 per cent of this total.^[64][65] In 2023, Canada exported $376 million of maple syrup to the United States, $47.8 million to Germany, $31.6 million to France, and $30.2 million to the UK, exporting to 68 countries in total.^[66]

As of 2022, Quebec accounts for 91.6 per cent of maple syrup produced in Canada, followed by New Brunswick at 4.7 per cent and Ontario at 3.4 per cent.^[67] However, 96.8 per cent of exported Canadian maple syrup originated from Quebec, whereas 2.6 per cent of exported syrup originated from New Brunswick, and the remaining 0.6 per cent from all other provinces.^[67] Ontario holds the most maple syrup farms in Canada outside of Quebec, with 389 maple syrup producers in 2021.^[67] This is followed by New Brunswick, with 114 maple syrup producers; and Nova Scotia, with 39 maple syrup producers.^[67]

As of 2016, Quebec had some 7,300 producers working with 13,500 farmers, collectively making over 30 million litres (8 million US gallons) of syrup.^[64][68] Production in Quebec is controlled through a supply management system, with producers receiving quota allotments from the government sanctioned Quebec Maple Syrup Producers (QMSP; Les Producteurs et productrices acéricoles du Québec), which also maintains reserves of syrup,^[64][69] although there is a black-market trade in Quebec product.^[64][70][71] In 2017, the QMSP mandated increased output of maple syrup production, attempting to establish Quebec’s dominance in the world market.^[64][65]

The Canadian provinces of Manitoba and Saskatchewan produce maple syrup using the sap of the box elder or Manitoba maple (Acer negundo).^[3] In 2011, there were 67 maple syrup producers in Manitoba and 24 in Saskatchewan.^[68] A Manitoba maple tree’s yield is usually less than half that of a similar sugar maple tree.^[72] Manitoba maple syrup has a slightly different flavour from sugar-maple syrup, because it contains less sugar and the tree’s sap flows more slowly. British Columbia is home to a growing maple sugar industry using sap from the bigleaf maple, which is native to the West Coast of the United States and Canada.^[73] In 2011, there were 82 maple syrup producers in British Columbia.^[68]

Vermont has long been the largest US producer, with a record 9.5 million litres (2.5 million US gallons) produced in 2022.^[74] In 2019 it led with over 7.8 million litres (2.07 million US gallons), followed by New York with 3.1 million L (820,000 US gal) and Maine with 2.2 million L (580,000 US gal). Wisconsin, Ohio, New Hampshire, Michigan, Pennsylvania, Massachusetts and Connecticut all produced marketable quantities of maple syrup.^[75]

Maple syrup has been produced on a small scale in some other countries, notably Japan and South Korea.^[76] However, in South Korea in particular, it is traditional to consume maple sap, called gorosoe, instead of processing it into syrup.^[77]

Markings

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Under Canadian maple product regulations, containers of maple syrup must include the words “maple syrup”, its grade name and net quantity in litres or millilitres, on the main display panel with a minimum font size of 1.6 mm.^[78][79] If the maple syrup is of Canada Grade A level, the name of the colour class must appear on the label in both English and French.^[78] Also, the lot number or production code, and either: (1) the name and address of the sugar bush establishment, packing or shipper establishment, or (2) the first dealer and the registration number of the packing establishment, must be labelled on any display panel other than the bottom.^[78][79]

Grades

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See also: Food grading

Following an effort from the International Maple Syrup Institute (IMSI) and many maple syrup producer associations, both Canada and the United States have altered their laws regarding the classification of maple syrup to be uniform. Whereas in the past each state or province had their own laws on the classification of maple syrup, now those laws define a unified grading system. This had been a work in progress for several years, and most of the finalization of the new grading system was made in 2014. The Canadian Food Inspection Agency (CFIA) announced in the Canada Gazette on 28 June 2014 that rules for the sale of maple syrup would be amended to include new descriptors, at the request of the IMSI.^[80]

As of 31 December 2014, the CFIA^[81] and as of 2 March 2015, the United States Department of Agriculture (USDA) Agricultural Marketing Service^[82] issued revised standards intended to harmonize Canadian and United States regulations on the classification of maple syrup as follows:

• Grade A
  • Golden colour and delicate taste
  • Amber colour and rich taste
  • Dark colour and robust taste
  • Very dark colour and strong taste
• Processing grade
• Substandard

As long as maple syrup does not have an off-flavour, is of a uniform colour, and is free from turbidity and sediment, it can be labelled as one of the A grades. If it exhibits any problems, it does not meet Grade A requirements, and then must be labelled as “processing grade” maple syrup and may not be sold in containers smaller than 20 litres (5 US gal).^[80][82] If maple syrup does not meet the requirements of processing-grade maple syrup (including a fairly characteristic maple taste), it is classified as substandard.^[80][82]

This grading system was accepted and made law by most maple-producing states and provinces, and became compulsory in Canada as of 13 December 2016.^[83] Vermont, in an effort to “jump-start” the new grading regulations, adopted the new grading system as of 1 January 2014, after the grade changes passed the US Senate and House in 2013. Maine passed a bill to take effect as soon as both Canada and the United States adopted the new grades. In New York, the new grade changes became law on 1 January 2015. New Hampshire did not require legislative approval and so the new grade laws became effective as of 16 December 2014, and producer compliance was required as of 1 January 2016.^[84]

Golden and amber grades typically have a milder flavour than dark and very dark, which are both dark and have an intense maple flavour.^[85] The darker grades of syrup are used primarily for cooking and baking, although some specialty dark syrups are produced for table use.^[86] Syrup harvested earlier in the season tends to yield a lighter colour.^[87] With the new grading system, the classification of maple syrup depends ultimately on its internal transmittance at 560 nm wavelength through a 10 mm sample. Golden must have 75 per cent or more transmittance, amber must have 50.0 to 74.9 per cent transmittance, dark must have 25.0 to 49.9 per cent transmittance, and very dark is any product having less than 25.0 per cent transmittance.^[82]

Old grading system

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In Canada, maple syrup was classified prior to 31 December 2014 by the Canadian Food Inspection Agency (CFIA) as one of three grades, each with several colour classes:^[80]

• Canada No. 1, including
  • Extra light
  • Light
  • Medium
• No. 2 amber
• No. 3 dark or any other ungraded category

Producers in Ontario or Quebec may have followed either federal or provincial grading guidelines.^[80] Quebec’s and Ontario’s guidelines differed slightly from the federal:

• there were two “number” categories in Quebec
  • Number 1, with four colour classes
  • Number 2, with five colour classes^[88]
• As in Quebec, Ontario’s producers had two “number” grades:
  • Number 1, with three colour classes
  • Number 2, with one colour class, which was typically referred to as “Ontario Amber” when produced and sold in that province only^[89]

A typical year’s yield for a maple syrup producer will be about 25 to 30 per cent of each of the #1 colours, 10 per cent #2 amber, and 2 per cent #3 dark.^[38]

The United States used different grading standards ⁠— ⁠some states still do as they await state regulation. Maple syrup was divided into two major grades:

• Grade A:
  • Light amber (sometimes known as fancy)
  • Medium amber
  • Dark amber
• Grade B.

In Massachusetts, the Grade B was renamed “Grade A Very Dark, Strong Taste”^[90]

The Vermont Agency of Agriculture Food and Markets used a similar grading system of colour, and is roughly equivalent, especially for lighter syrups, but using letters: “AA”, “A”, etc.^[91][92] The Vermont grading system differed from the US system in maintaining a slightly higher standard of product density (measured on the Baumé scale). New Hampshire maintained a similar standard, but not a separate state grading scale. The Vermont-graded product had 0.9 per cent more sugar and less water in its composition than US-graded. One grade of syrup not for table use, called commercial or Grade C, was also produced under the Vermont system.^[85]

Packing regulations

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In Canada, the packing of maple syrup must follow the “Packing” conditions stated in the maple products regulations, or utilize the equivalent Canadian or imported grading system.^[78]

As stated in the maple products regulations, Canadian maple syrup can be classified as “Canadian Grade A” and “Canadian Processing Grade”. Any maple syrup container under these classifications should be filled to at least 90% of the bottle size while still containing the net quantity of syrup product as stated on the label. Every container of maple syrup must be new if it has a capacity of 5 litres or less or is marked with a grade name. Every container of maple sugar must also be new if it has a capacity of less than 5 kg or is either exported out of Canada or conveyed from one province to another.^[78]

Each maple syrup product must be verified clean if it follows a grade name or if it is exported out of the province in which it was originally manufactured.^[78]

Nutrition

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Nutritional value per 100 g (3.5 oz)
Energy	1,088 kJ (260 kcal)
Carbohydrates	67 g
Sugars	60.4
Fat	0.06 g
Protein	0.04 g
showVitamins and minerals
Other constituents	Quantity
Water	32.4 g
Link to USDA Database entry
†Percentages estimated using US recommendations for adults,[93] except for potassium, which is estimated based on expert recommendation from the National Academies.[94]

The basic ingredient in maple syrup is the sap from the xylem of sugar maple or various other species of maple trees. It consists primarily of sucrose and water, with small amounts of the monosaccharides glucose and fructose from the inverted sugar created in the boiling process.^[95][96]

In a 100g amount, maple syrup provides 260 calories and is composed of 32 per cent water by weight, 67 per cent carbohydrates (90 per cent of which are sugars), and no appreciable protein or fat (table). Maple syrup is generally low in overall micronutrient content, although manganese and riboflavin are at high levels along with moderate amounts of zinc and calcium (right table). It also contains trace amounts of amino acids which increase in content as sap flow occurs.^[97]

Maple syrup contains a wide variety of polyphenols and volatile organic compounds, including vanillin, hydroxybutanone, lignans, propionaldehyde, and numerous organic acids.^{[98][99][100]} It is not yet known exactly all compounds responsible for the distinctive flavour of maple syrup,^[39] although primary flavour-contributing compounds are maple furanone (5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone), strawberry furanone, and maltol.^[101] New compounds have been identified in maple syrup, one of which is quebecol, a natural phenolic compound created when the maple sap is boiled to create syrup.^[102] Its sweetness derives from a high content of sucrose (99% of total sugars).^[96] Its brown colour – a significant factor in the appeal and quality grading of maple syrup – develops during thermal evaporation.^[103]

One author described maple syrup as “a unique ingredient, smooth- and silky-textured, with a sweet, distinctive flavour – hints of caramel with overtones of toffee will not do – and a rare colour, amber set alight. Maple flavour is, well, maple flavour, uniquely different from any other.”^[62] Agriculture Canada has developed a “flavour wheel” that details 91 unique flavours that can be present in maple syrup. These flavours are divided into 13 families: vanilla, burnt, milky, fruity, floral, spicy, foreign (deterioration or fermentation), foreign (environment), maple, confectionery, plant (herbaceous), plant (forest, humus or cereals), and plant (ligneous).^[104][105] These flavours are evaluated using a procedure similar to wine tasting.^[106] Other culinary experts praise its unique flavour.^{[107][108][109]} Environmental factors, including weather and soil type, impact flavor.^[110]

Maple syrup and its various artificial imitations are widely used as toppings for pancakes, waffles, and French toast in North America. They can also be used to flavour a variety of foods, including fritters, ice cream, hot cereal, fresh fruit, bacon, and sausages. It is also used as sweetener for granola, applesauce, baked beans, candied sweet potatoes, winter squash, cakes, pies, breads, tea, coffee, and hot toddies.^[111]

Imitations

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In Canada, maple syrup must be made entirely from maple sap, and syrup must have a density of 66° on the Brix scale to be marketed as maple syrup.^[38] In the United States, maple syrup must be made almost entirely from maple sap, although small amounts of substances such as salt may be added.^[112] Labelling laws prohibit imitation syrups from having “maple” in their names unless the finished product contains 10 per cent or more of natural maple syrup.^[112]

Table syrup, also known as pancake syrup and waffle syrup, is often used as a substitute for maple syrup. Table syrups are mostly made using corn syrup and high-fructose corn syrup, giving them a less complex and more artificial flavour compared to maple syrup.^[113] In the United States, consumers generally prefer imitation syrups, likely because of the significantly lower cost and sweeter flavour;^[114][115] they typically cost about $2 per litre ($8 per US gallon), whereas authentic maple syrup costs $11–$16 per litre ($40–$60 per US gallon) as of 2015.^[115]

In 2016, maple syrup producers from nine US states petitioned the Food and Drug Administration (FDA) to regulate labelling of products containing maple syrup or using the word “maple” in manufactured products, indicating that imitation maple products contained insignificant amounts of natural maple syrup.^[116] In September 2016, the FDA published a consumer advisory to carefully inspect the ingredient list of products labelled as “maple”.^[117]

Cultural significance

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Maple products are considered emblematic of Canada, and are frequently sold in tourist shops and airports as souvenirs from Canada. The sugar maple’s leaf has come to symbolize Canada, and is depicted on the country’s flag.^[118] Several US states, including West Virginia, New York, Vermont, and Wisconsin, have the sugar maple as their state tree.^[119] A scene of sap collection is depicted on the Vermont state quarter, issued in 2001.^[120]

Maple syrup and maple sugar were used during the American Civil War and by abolitionists in the years before the war because most cane sugar and molasses were produced by Southern slaves.^[114][121] Because of food rationing during the Second World War, people in the northeastern United States were encouraged to stretch their sugar rations by sweetening foods with maple syrup and maple sugar,^[19] and recipe books were printed to help housewives employ this alternative source