Making Walnut Oil

The Old Masters would have ground most of their own pigments, or in the case of the more successful ones-had assistants do the work them. Along with this they would have had an intricate knowledge of the best ways to prepare each pigment. They could maximize the brilliance and longevity of each color.

Some of the mineral pigments that I'm preparing to make are better suited to different binding mediums. The linseed oil that I've used to mix most of my paints is not really compatible with these colors. So this week I started preparing some walnut oil.

The process is the same as for preparing linseed oil. The walnut oil will need to be cleansed of natural contaminants before I can use it. I will do this using water and sunlight.















Here is the walnut oil I'm going to be using. This is a decent California brand, bought from the grocery store.

I added distilled water into the oil, shook the mixture thoroughly, and left it out under the sun.















I waited about 3 days. The water and oil have separated. The mucilage and other contaminants are trapped in between the two.















Here's a close up shot. The layer of mucilage is really visible here.















Yuck. A top down shot that really shows the mucilage well. It has already discolored noticeably from only a few days in the sun. This would be a major contributor to yellowing and other discoloration in a painting if not first removed.















I very carefully removed the oil from the top using a pipette. The oil is noticeably clearer now than before. I will repeat the process several more times until I'm satisfied I've gotten it clean.

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.