Linseed oil is a vegetable oil produced from flaxseed. It has yellowish color and used as a drying oil in paints, varnishes etc. Flaxseed contains about 40% linseed oil.

Uses of Linseed Oil:

• Linseed oil is use mainly as paint-drying oil. In making paints the oil is mixed with colorings, a volatile thinner, and a drier. After the paint is spread, the thinner evaporates, and the oil reacts with oxygen, forming a tough elastic film. The drier speeds up film formation. Oxidation continues slowly after the paint has dried and eventually destroys the film.
• Linseed oil is used also in varnishes, enamels, putty, leather treatment, linoleum, oilcloth, printing inks and industrial lubricants.
• It can be used to waterproof (sealants) and toughen paper and fabrics
• It is also use as ingredient in liniments and medicinal soaps as an emollient.

How Linseed oil is obtained: The cleaned flaxseed is crushed between heavy steel rollers. The mashed meal is then heated by steam, and the oil is forced in hydraulic presses or screw expellers. Solvent extraction can be used to recover additional oil. The press cake, which is a by-product is high in protein and is use as a livestock food.

Forms of Linseed Oil:

• Raw linseed oil - is a filtered flax seed oil and packaged with no additional additives or preservatives. Raw linseed oil dries very slowly, and it takes weeks to fully cure, therefore the use of raw linseed oil should limited to the insides of wood gutters, chopping blocks, sawhorses, and other items exposed to the elements where drying time is not a consideration. Slow drying has some benefits also, since this allows the paint to "level" itself, it gives the finish product a smoother finish with fewer brush marks.

• Boiled linseed oil - to make the boiled linseed oil used in paints, the raw oil is heated under reduced pressure. Heating the oil makes it polymerize and oxidize, effectively making it thicker and shortening the drying time. Boiled linseed oil is used as a paint binder or as a wood finish on its own.

Problems with linseed oil:

• Garden furniture treated with linseed oil can encourage mildew growth because it is not completely denatured
• Multiple coats of linseed oil are sticky and difficult to remove fully for refinishing.