Linseed oil

Linseed oil is a yellowish drying oil derived from the dried ripe seeds of the flax plant (Linum usitatissimum, Linaceae). It is obtained by pressing, followed by an optional stage of solvent extraction. Cold-pressed oil obtained without solvent extraction is marketed as flaxseed oil.

As a paint binder

Linseed oil is the most commonly used carrier in oil paint.

As a wood finish

When used as a wood finish, linseed oil does not cover the surface as varnish does, but soaks into the (visible and microscopic) pores, leaving a shiny but not glossy surface that shows off the grain. Wood treated with linseed oil only is resistant to denting, and scratches are easily repaired, but the wood and oil surface is not as hard as a modern varnish, and it slowly absorbs moisture if allowed to stay wet. Soft wood benefits from the protection from denting but requires more applications and even more drying time than harder wood does, if the grain is to be completely filled. The oil penetrates deeply and fills the grain, because it dries slowly and shrinks little or not at all on hardening. It is a traditional finish for gun stocks, however a very fine finish may require months to obtain. Oiled wood is yellowish and darkens with age.

As a nutritional supplement

Flaxseed oil is suitable for human consumption, and is used as a nutritional supplement. It is rich in omega-3 fatty acids, especially alpha-linolenic acid, which appears to be beneficial for heart disease, inflammatory bowel disease, arthritis and a variety of other health conditions. Flaxseed also contains a group of chemicals called lignans that may play a role in the prevention of cancer. ^*

Additional uses

Animal feeds
Putty
Sealants
Caulking compounds
Brake linings
Linoleum
Earthen floors
Textiles
Bicycle repair as a thread fixative and lubricant for the spokes of bicycle wheels
Foundry products
Leather treatment
Polishes, varnishes and oil paints
Animal care products
Wood preservation
Synthetic resins
Oil painting medium: Includes such varieties as Cold Pressed, Bleached and Refined.
Treatment for the raw willow wood used to make cricket bats. Linseed oil has a special cultural place in cricket-playing countries.

Boiled linseed oil

Boiled linseed oil is used as a paint binder or as a wood finish on its own. Heating the oil makes it polymerize or oxidise more readily, effectively shortening the drying time. Today most products labeled as "boiled linseed oil" are a combination of raw linseed oil, petroleum-based solvent and metallic dryers. The use of metallic dryers makes boiled linseed oil inedible. There are some products available that contain only heat-treated linseed oil. These are usually labeled as "polymerized" oils though some may still be labeled as boiled.

Nutrient content

Nutrition information from a typical commerically available flaxseed oil:

Per 1 Tbsp (14 g)