Linseed Oil is a fantastically versatile product. It has a huge range of applications, from use in DIY, to health food supplementation to playing a role in the making of linoleum flooring.
The oil is made by pressing the dried, ripened seeds of the flax plant (Linum usitatissimum). The seeds can be warm-pressed, which gives a higher yield, or cold-pressed, which results in fewer impurities and is usually a better option.
Linseed oil is classified as a drying oil, due to its high content of di- and tri-unsaturated esters. Because of these properties, linseed oil can also be combined with other oils.
Linseed oil has so many uses it’s available to buy in a variety of different forms, with a variety of different names. Here’s a guide to the different types of linseed oil and which might be most suitable for your project.
Flaxseed or flax oil
Flaxseed or flax oil is generally the name given to linseed oil that’s pure enough to be edible. We’d advise checking packaging very carefully to ensure the version you’ve got is marked as food safe, as many types of flaxseed and linseed oil have added ingredients that are not meant for consumption.
Raw linseed oil
Raw linseed oil is unprocessed linseed oil without any added driers or thinners. If you choose to use raw linseed oil as a wood treatment you will need to use very thin coats as it doesn’t dry particularly well.
Much of the low cost linseed oil on the market falls into this category. Low cost linseed oils or oils from many hardware stores are also generally made from warm-pressed oil containing a lot of impurities and proteins. We don’t recommend using this type of linseed oil in linseed paint or as a wood treatment as there’s a high risk of mould and algae growth.
Boiled linseed oil
This is when raw linseed oil is boiled with a small quantity of natural drying agents such as cobalt or manganese. Heating the oil with these agents changes its viscosity and shortens the drying time. Boiled oil can be used to treat furniture and indoor woodwork. It also is the main ingredient for exterior linseed paint.
Double-boiled linseed oil
You may also come across ‘double-boiled’ linseed oil, but this is generally marketing-spiel and not a genuine description. There’s no benefit to boiling linseed oil twice, so there’s no reason for manufacturers to do so.
Stand oil or polymerised linseed oil
Stand oil is a specialised form of boiled linseed oil. It’s made by heating raw linseed oil in a vacuum at close to 300°C for a few days. This creates a very thick oil with more of an elastic coating than standard boiled linseed oil.
This type of linseed oil is usually used by artists to achieve an even finish or certain paint techniques. It’s not usually used for wood treatment as the thickness of stand oil would be difficult to work with over a large surface area.
Sun-thickened or sun-bleached linseed oil
Raw linseed oil is sometimes thickened by setting it in large trays and exposing it to sunlight for a few months. This can increase the elasticity of the oil and reduce yellowing.
Sun-thickened linseed oil isn’t usually used on its own but is useful as an additive in linseed paint when an even finish is necessary (again, this might be more relevant to artists than people refinishing window frames).
Danish oil is usually made from a blend of boiled or stand linseed oil and tung oil. It’s often used either as a wood primer or to create a hard-wearing satin finish. Unfortunately, as there’s no defined recipe for Danish oil it can vary wildly in grade and quality.
Tar oil is made by combining raw linseed oil with tar. This is not a true linseed oil as tar is derived from the roots of coniferous tree species, not flax. Adding raw linseed oil to tar makes it thinner, which means it is easier to apply without needing to be heated.
Specialist linseed oil for exterior wood and timber
Though boiled linseed oil can give a great clear protective finish on wood, in many cases a specially formulated linseed oil might be more suitable.
Our Nourish Wood Oil has been developed to dry more quickly and show less yellowing. Unlike raw and boiled linseed oil, it also contains anti-mould agents for added protection.
Things to keep in mind
Whichever type of linseed oil you opt for, it’s important to make sure it’s stored and disposed of correctly.
Linseed oil has a high di- and tri-unsaturated ester content, which means it can react rapidly with oxygen in the air. Because linseed oil products can dry out quickly when exposed, it’s important to always store them in airtight containers.