Linseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colourless to yellowish oil obtained from the dried, ripened seeds of the

flax Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. Textiles made from flax are known in ...

plant (''Linum usitatissimum''). The oil is obtained by pressing, sometimes followed by

solvent extraction A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

. Owing to its polymer-forming properties, linseed oil is often blended with combinations of other oils,

resins In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

s as an impregnator, drying oil finish or varnish in

wood finishing Wood finishing refers to the process of refining or protecting a wooden surface, especially in the production of furniture where typically it represents between 5 and 30% of manufacturing costs. Finishing is the final step of the manufacturing ...

, as a

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...

binder in

oil paint Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and va ...

s, as a

plasticizer A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture. Plasticiz ...

and hardener in

putty Putty is a material with high plasticity, similar in texture to clay or dough, typically used in domestic construction and repair as a sealant or filler. Although some types of putty (typically those using linseed oil) slowly polymerise and be ...

, and in the manufacture of

linoleum Linoleum, sometimes shortened to lino, is a floor covering made from materials such as solidified linseed oil (linoxyn), Pine Resin, pine resin, ground Cork (material), cork dust, sawdust, and mineral fillers such as calcium carbonate, most com ...

. Linseed oil use has declined over the past several decades with increased availability of synthetic

alkyd An alkyd is a polyester resin modified by the addition of fatty acids and other components. Alkyds are derived from polyols and organic acids including dicarboxylic acids or carboxylic acid anhydride and triglyceride oils. The term ''alkyd'' is a m ...

resins—which function similarly but resist yellowing. Linseed oil is an

edible oil Cooking oil is plant, animal, or synthetic liquid fat used in frying, baking, and other types of cooking. It is also used in food preparation and flavoring not involving heat, such as salad dressings and bread dips, and may be called edible oil ...

in demand as a dietary supplement, as a source of

α-Linolenic acid ''alpha''-Linolenic acid (ALA), also known as α-Linolenic acid (from Greek language, Greek ''alpha'' meaning "first" and ''linon'' meaning flax), is an omega-3 fatty acid, ''n''−3, or omega-3, essential fatty acid. ALA is found in many seeds ...

, an

omega-3 fatty acid Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or ''n''−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond, three atoms away from the terminal methyl group in their chem ...

. In parts of Europe, it is traditionally eaten with potatoes and quark.

Structure and composition

: 450px, Representative triglyceride found in a linseed oil, a triester ( linoleic_acid,_alpha-linolenic_acid.html" ;"title="linoleic acid">linoleic acid, alpha-linolenic_acid,_and_oleic_acid.html" ;"title="alpha-linolenic acid">alpha-linolenic acid, and oleic_acid..html" ;"title="oleic acid">oleic acid.">oleic acid">oleic acid. Linseed oil is a

triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''wikt:tri-#Prefix, tri-'' and ''glyceride''). Triglycerides are the main constituents of body fat in humans and other ...

, like other fats. Linseed oil is distinctive for its unusually large amount of

α-linolenic acid ''alpha''-Linolenic acid (ALA), also known as α-Linolenic acid (from Greek language, Greek ''alpha'' meaning "first" and ''linon'' meaning flax), is an omega-3 fatty acid, ''n''−3, or omega-3, essential fatty acid. ALA is found in many seeds ...

, which oxidises in air. The fatty acids in a typical linseed oil are of the following types: *The triply unsaturated α-linolenic acid (51.9–55.2%), *The saturated acids

palmitic acid Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and microorganisms.Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The Li ...

(about 7%) and

stearic acid Stearic acid ( , ) is a saturated fatty acid with an 18-carbon chain. The IUPAC name is octadecanoic acid. It is a waxy solid and its chemical formula is C17H35CO2H. Its name comes from the Greek word στέαρ "''stéar''", which means tallow. ...

(3.4–4.6%), *The monounsaturated

oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega ...

(18.5–22.6%), *The doubly unsaturated

linoleic acid Linoleic acid (LA) is an organic compound with the formula COOH(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are cis-trans isomerism, ''cis''. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 ''cis''-9,12. A linoleate is a salt (chem ...

(14.2–17%).

Drying properties

Having a high content of di- and tri-unsaturated esters, linseed oil is susceptible to polymerization reactions upon exposure to oxygen in air. This polymerization, which is called "

drying Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. To be consider ...

", results in the rigidification of the material. To prevent premature drying, linseed oil-based products (oil paints, putty) are stored in airtight containers. Rags soaked with linseed oil stored pose fire hazard because they provide a large surface area for rapid

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

. The oxidation of linseed oil is exothermic, which may lead to

spontaneous combustion Spontaneous combustion or spontaneous ignition is a type of combustion which occurs by self-heating (increase in temperature due to exothermic internal reactions), followed by thermal runaway (self heating which rapidly accelerates to high te ...

. In 1991,

One Meridian Plaza One Meridian Plaza, formerly known as the Fidelity Mutual Life Building, Three Girard Plaza and Three Mellon Bank Center, was a 38- story high-rise office building in Philadelphia, Pennsylvania, United States. The tower was designed by Vincent K ...

, in

Philadelphia Philadelphia, often called Philly, is the largest city in the Commonwealth of Pennsylvania, the sixth-largest city in the U.S., the second-largest city in both the Northeast megalopolis and Mid-Atlantic regions after New York City. Sinc ...

, was severely damaged in a fire, in which three firefighters perished, thought to be caused by rags soaked with linseed oil.

Applications

Most applications of linseed oil exploit its drying properties, i.e., the initial material is liquid or at least pliable and the aged material is rigid but not brittle. The water-repelling (hydrophobic) nature of the resulting

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

-based material is advantageous.

Paint binder

Linseed oil is the carrier used in

. It can also be used as a painting medium, making oil paints more fluid, transparent and glossy. It is available in varieties such as cold-pressed, alkali-refined, sun-bleached, sun-thickened, and polymerised (stand oil). The introduction of linseed oil was a significant advance in the technology of oil painting.

Putty

Traditional glazing

, consisting of a paste of

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...

powder and linseed oil, is a sealant for glass windows that hardens within a few weeks of application and can then be painted over. The durability of putty is owed to the drying properties of linseed oil.

Wood finish

When used as a

wood finish Wood finishing refers to the process of refining or protecting a wooden surface, especially in the production of furniture where typically it represents between 5 and 30% of manufacturing costs. Finishing is the final step of the manufacturing ...

, linseed oil dries slowly and shrinks little upon hardening. A linseed oil finish is easily scratched and liquid water penetrates a linseed oil finish in mere minutes, and water vapour bypasses it almost completely.

Garden furniture Garden furniture, also called patio furniture or outdoor furniture, is a type of furniture specifically designed for outdoor use. It is typically made of weather-resistant materials such as aluminium which is rust-proof. History The oldes ...

treated with linseed oil may develop

mildew Mildew is a form of fungus. It is distinguished from its closely related counterpart, mould, largely by its colour: moulds appear in shades of black, blue, red, and green, whereas mildew is white. It appears as a thin, superficial growth consi ...

. Oiled wood may be yellowish and is likely to darken with age. Even though the oil feels dry to the touch, studies show linseed oil does not fully cure. Linseed oil is a common finish for wooden items, though very fine finish may require months to obtain. Studies show the fatty-acid structure of linseed oil has problems cross-linking and oxidizing, frequently turning black. It is no longer encouraged to use linseed oil to recondition and regenerate finishes because of the cross-linking oxidization that occurs.

Gilding

Boiled linseed oil is used as sizing in traditional oil

gilding Gilding is a decorative technique for applying a very thin coating of gold over solid surfaces such as metal (most common), wood, porcelain, or stone. A gilded object is also described as "gilt". Where metal is gilded, the metal below was tradi ...

to adhere sheets of gold leaf to a substrate (parchment, canvas,

Armenian bole Armenian bole, also known as bolus armenus or bole armoniac, is an earthy clay, usually red, native to Armenia but also found in other places. The term Armenian was later referred to a specific quality of the clay. Originally used in medication, it ...

, etc.). It has a much longer working time than water-based size and gives a firm smooth surface that is adhesive enough in the first 12–24 hours after application to cause the gold to attach firmly to the intended surface.

Linoleum

Linseed oil is used to bind wood dust, cork particles, and related materials in the manufacture of the floor covering

. After its invention in 1860 by

Frederick Walton Frederick Edward Walton (13 March 183416 May 1928), was an English manufacturer and inventor whose invention of Linoleum in Chiswick was patented in 1863. He also invented Lincrusta in 1877. Early life Walton was born in 1834, near Halifax. ...

, linoleum, or 'lino' for short, was a common form of domestic and industrial floor covering from the 1870s until the 1970s when it was largely replaced by PVC ('vinyl') floor coverings. However, since the 1990s, linoleum is returning to favor, being considered more environmentally sound than PVC. Linoleum has given its name to the printmaking technique

linocut Linocut, also known as lino print, lino printing or linoleum art, is a printmaking technique, a variant of woodcut in which a sheet of linoleum (sometimes mounted on a wooden block) is used for a relief surface. A design is cut into the linoleum s ...

, in which a relief design is cut into the smooth surface and then inked and used to print an image. The results are similar to those obtained by

woodcut Woodcut is a relief printing technique in printmaking. An artist carves an image into the surface of a block of wood—typically with gouges—leaving the printing parts level with the surface while removing the non-printing parts. Areas that ...

printing.

Nutritional supplement and food

Raw cold-pressed linseed oil – commonly known as flax seed oil in nutritional contexts – is easily oxidized, and rapidly becomes rancid, with an unpleasant

odour An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sense ...

, unless

refrigerated The term refrigeration refers to the process of removing heat from an enclosed space or substance for the purpose of lowering the temperature.International Dictionary of Refrigeration, http://dictionary.iifiir.org/search.phpASHRAE Terminology, ht ...

. Linseed oil is not generally recommended for use in cooking. Alpha linolenic acid (ALA) while bound to flaxseed ALA can withstand temperatures up to 175 °C (350 °F) for two hours. Food-grade flaxseed oil is cold-pressed, obtained without solvent extraction, in the absence of oxygen, and marketed as edible flaxseed oil. Fresh, refrigerated and unprocessed, linseed oil is used as a

nutritional supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources or that are synthetic in order ...

and is a traditional European ethnic food, highly regarded for its nutty flavor. Regular flaxseed oil contains between 57% and 71% polyunsaturated fats (

alpha-linolenic acid ''alpha''-Linolenic acid (ALA), also known as α-Linolenic acid (from Greek ''alpha'' meaning "first" and ''linon'' meaning flax), is an ''n''−3, or omega-3, essential fatty acid. ALA is found in many seeds and oils, including flaxseed, wa ...

). Plant breeders have developed flaxseed with both higher ALA (70%) and very low ALA content (< 3%). The USFDA granted generally recognized as safe (GRAS) status for high alpha linolenic flaxseed oil.

Nutrient content

Nutrition information from the Flax Council of Canada. Per 1 tbsp (14 g) * Calories: 126 * Total

fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...

: 14 g *

Omega-3 Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or ''n''−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond, three atoms away from the terminal methyl group in their chem ...

: 8 g *

Omega-6 Omega-6 fatty acids (also referred to as ω-6 fatty acids or ''n''-6 fatty acids) are a family of polyunsaturated fatty acids that have in common a final carbon-carbon double bond in the ''n''-6 position, that is, the sixth bond, counting from ...

: 2 g *

Omega-9 Omega-9 fatty acids (ω−9 fatty acids or ''n''−9 fatty acids) are a family of unsaturated fatty acids which have in common a final carbon–carbon double bond in the omega−9 position; that is, the ninth bond from the methyl end of the fat ...

: 3 g Flax seed oil contains no significant amounts of protein, carbohydrates or fibre.

Comparison to other vegetable oils

Additional uses

* Animal care products * Bicycle maintenance as a thread fixative, rust inhibitor and lubricant *

Composition ornament Composition ornament ("compo") is a mouldable thermoplastic compound, consisting of powdered chalk mixed with collagen (hide glue), resin (pine rosin) and linseed oil; worked either by hand or more usually pressed into moulds to produce decorative ...

for moulded decoration *

Earthen floor An earthen floor, also called an adobe floor, is a floor made of dirt, raw earth, or other unworked ground materials. It is usually constructed, in modern times, with a mixture of sand, finely chopped straw and clay, mixed to a thickened consiste ...

s * Animal feeds * Industrial lubricant *

Leather Leather is a strong, flexible and durable material obtained from the tanning, or chemical treatment, of animal skins and hides to prevent decay. The most common leathers come from cattle, sheep, goats, equine animals, buffalo, pigs and hogs, ...

treatment *

Oilcloth Oilcloth, also known as enameled cloth or American cloth, is close-woven cotton duck or linen cloth with a coating of boiled linseed oil to make it waterproof. Manufacture Boiled linseed oil was prepared by a long boiling of linseed oil with m ...

Particle detector In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify ionizing particles, such as those produced by nuc ...

s *

Textile Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...

s *

Wood preservation Wood easily degrades without sufficient preservation. Apart from structural wood preservation measures, there are a number of different chemical preservatives and processes (also known as "timber treatment", "lumber treatment" or "pressure treat ...

(including as an active ingredient of

Danish oil Danish oil is a wood finishing oil, often made of tung oil or polymerized linseed oil. Because there is no defined formulation, its composition varies among manufacturers. Danish oil is a hard drying oil, meaning it can polymerize into a sol ...

) * Cookware seasoning * Plant protection

Modified linseed oils

Stand oil

Stand oil is generated by heating linseed oil near 300 °C for a few days in the complete absence of air. Under these conditions, the polyunsaturated fatty esters convert to conjugated

diene In organic chemistry a diene ( ) (diolefin ( ) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alk''ene'' units, with the standard prefix ''di'' of systematic nomenclature. ...

s, which then undergo Diels-Alder reactions, leading to crosslinking. The product, which is highly viscous, gives highly uniform coatings that "dry" to more elastic coatings than linseed oil itself.

Soybean oil Soybean oil (British English: soyabean oil) is a vegetable oil extracted from the seeds of the soybean (''Glycine max''). It is one of the most widely consumed cooking oils and the second most consumed vegetable oil. As a drying oil, processed s ...

can be treated similarly, but converts more slowly. On the other hand,

tung oil Tung oil or China wood oil is a drying oil obtained by pressing the seed from the nut of the tung tree (''Vernicia fordii''). The oil and its use are believed to have originated in ancient China and appear in the writings of Confucius from ab ...

converts very quickly, being complete in minutes at 260 °C. Coatings prepared from stand oils are less prone to yellowing than are coatings derived from the parent oils.

Boiled linseed oil

Boiled linseed oil is a combination of raw linseed oil, stand oil (see above), and metallic

oil drying agent An oil drying agent, also known as siccative, is a coordination compound that accelerates ( catalyzes) the hardening of drying oils, often as they are used in oil-based paints. This so-called "drying" (actually a chemical reaction that produces an ...

s (catalysts to accelerate drying). In the

Medieval era In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...

, linseed oil was boiled with

lead oxide Lead oxides are a group of inorganic compounds with formulas including lead (Pb) and oxygen (O). Common lead oxides include: * Lead(II) oxide, PbO, litharge (red), massicot (yellow) * Lead(II,IV) oxide Lead(II,IV) oxide, also called red lead o ...

(litharge) to give a product called boiled linseed oil. The lead oxide forms lead "soaps" (lead oxide is alkaline) which promotes hardening (polymerisation) of linseed oil by reaction with atmospheric oxygen. Heating shortens its drying time.

Raw linseed oil

Raw linseed oil is the base oil, unprocessed and without driers or thinners. It is mostly used as a feedstock for making a boiled oil. It does not cure sufficiently well or quickly to be regarded as a

drying oil A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air, at room temperature. The oil hardens through a chemical reaction in which the components crosslink (and hence, polymerize) by the action of oxygen (no ...

. Raw linseed is sometimes used for oiling cricket bats to increase surface friction for better ball control. It was also used to treat leather flat belt drives to reduce slipping.

References

External links

* {{Authority control Vegetable oils Dietary supplements Visual arts materials Painting materials Wood finishing materials Oils Flax es:Linaza