Tuesday, October 6, 2009

Making Sun-Thickened Linseed Oil

Linseed oil is made from the seeds of the flax plant. It is the strongest of the drying oils suitable for oil painting. Oil is extracted from the seeds under extremely high heat and pressure. The oil is then refined using strong alkali chemicals. The process is cheap, has high yields, and is done on a massive scale by a few large producers. Most commercial artist's paints are made from this oil.

The traditional process of making oil was far different. It was cold pressed and purified without harsh chemicals, usually just water. The process was slow and had lower yields, so it was long ago abandoned by industry.

I began making my own linseed oil the older way several years ago. It is not difficult, only time-consuming. I buy only organic cold-pressed flaxseed oil. an edible health supplement. The oil should be unrefined, and not have any additives. Before the oil can be used, it should be filtered of impurities.

I pour the oil into glass jars about an inch high. Distilled water is added to the oil and the contents are shaken so that they are thoroughly mixed.

The closed jars are placed to sit under the sun for several days. Our roof has a nice flat shelf to one side, so I put my oil up there.

The oil and water will eventually separate. Impurities such as mucilage become trapped in the boundary layer between the water and oil. I carefully remove the oil off of the top. I filtered this batch about three times over.

Properly cleansed, the oil is placed out in the sun again. I pour the oil into small bowls, place them in an old box, and cover it with glass. I've put little spacers between the glass and box so that air can circulate inside easily.

The sun will oxidize the oil, so that it becomes thicker and will dry faster. How long this goes on is up to individual preference. A month is typically required during the summer to get a thick oil. Every day I remove the glass and stir the oil, so that no dry film can form on the surface

The finished product is crystal clear, and has been bleached by the sun to a pale, straw-color. I'm still amazed at how simple and effective this process is. Used in a painting medium, the oil will dry in a few days, versus weeks for the typical store bought variety.


Dave Cain said...

This is great. I've been messing with waxing cotton and a friend pointed me to your blog post. How did you learn this process? Thanks for sharing.

Zachary Kator said...

Dear Dave,

Many artists over the centuries documented the methods used in their craft, including how to make linseed oil. A handful of modern artists that I know of, have been trying to rediscover exactly how it was done. Thanks for the comments.

Keith Russell said...

I have Charles Eastlake's treatise on painting, and he talks about a linseed oil that was "clear as water"...but his method for making it wasn't as clear as your description, here. I'm definitely going to try this. Thanks!

Zachary Kator said...

I'm working on some new methods of refining the oil, and should be doing a post on it shortly. Thanks for the comments!

sarus said...

Does it work with walnut oil too? Thanks!

Zachary Kator said...


I wouldn't say I'm an expert on walnut oil, as I use very little. Walnut oil yellows much less than linseed oil so the need to filter it is much less great.

That being said, I have used this method to clean unfiltered walnut oil and it removed large amounts of mucilage from the oil.

Thanks for the comment!

Ruth Posthuma de Boer said...

Some say hot water, add salt, sand,
And there are many more recipes.
Your method sounds okay.
Any further deveopments?