Sunday, October 23, 2011

Linseed Oil, Part II

Using the best oil possible is key not only to making paint with the best handling qualities, but also ensuring that a painting ages gracefully. While linseed oil naturally yellows a certain extent over time, an inferior oil will be far worse. In the picture above, the unsightly brown goo is nothing more than linseed oil that has separated from the paint and oozed out of the tube. What is surprising is how awfully brown this modern oil has become.

Over the past month, I have set aside some time to improve my homemade linseed oil. My goal was to speed up and improve the process of refining the raw oil.

The key to speeding up the process was finding a more effective method of removing the heavy fatty acids, or mucilage contained in the raw, unfiltered oil. These impurities are the key cause of unsightly yellowing seen in oil. I wanted to filter the oil mechanically, without the resorting to the strong chemicals used in the production of commercial oil.

In the past I have cleaned my oil with water and sunlight, this method was time-consuming and had to be done in warm weather. Other historical practices suggested washing the oil with a mixture of sand, salt and water. This was also time consuming and repetitious.

A variation of this method substitutes sand for a mixture of diatomaceous earth and cristobalite. These are simple forms of silica, used as a harmless filter medium. The calcined form is easy to find unadulterated, as used in pool filters. The process is new to me, other artists such as Tad Spurgeon have been making their oil using this method for some time.

I mixed one part D.E. with two parts raw flax oil, added a pinch of salt and three parts water. The jars containing the oil were put in a warm spot and shaken periodically over the course of a few days, to disburse the mixture.

The early results were dramatic. Most of the filter mix has settled to the bottom of the jar. The heavy fatty acids have become trapped in the boundary layer between water and oil.

The oil was siphoned off the top, filtered and the process was repeated again several times with fresh ingredients. Salt was used only in the first cleaning.

Not being completely satisfied the oil was good enough, I put the oil on the roof and washed it a few times over several days with water.

Looking down through the jar shows an almost clear oil, very little mucilage remains.

The appearance of the oil has definitely changed.

The oil was put into a newly-built glass box on the roof, to briefly sun-bleach. It will then be set aside for awhile to age, before being put to use.


abuelitoluis said...

Hello. My name is Louis R. Velasquez. I invite you to view my website. Just Google the name Calcite Sun Oil.
Regarding your views and efforts on the oil we artists use.
1. You are correct in saying the oil is of extreme importance.
2. Correct in beginning with unrefined linseed/flax oil.
3. Water washing with or without salt is a waste of time, a waste of energy and a waste of good oil. Water washing with or without salt, sand, diatomaceous Earth or other inert substance is a complete waste and ineffective.
4. You are correct in that the mucilage must be removed from the unrefined oil. Modern industrial use of caustic lye chemicals such as sodium hydroxide damage the oil. Besides removing the mucilage (and note that even tis chemical process does not remove it all) it removes other important molecules of the oil.
5. You are grossly incorrect that the fatty acids must be removed. The fatty acids are a component of this 'miracle' vegetable oil that gives the oil it's pliability to endure centuries. Your use of the word to describe the fatty acids...calling them 'heavy' is incorrect. We're they heavy they would have dropped out of the oil of themselves. Science shows it is 2of the over 7 fatty acids in this oil that cause the yellow color of th oil. This coloring is fugitive and easily bleached by the ultraviolet rays in sunlight. Sunlight bounces and reflects and explains why any room in your house is illuminated without bing in direct sunlight. Oil paintings in rooms with sunlight do not turn yellow. The reason the oil in the jar ...oil that has had the mucilage removed...and previously sun yellow is because you are seeing that oil in concentration. Put one drop on a pure white plate and rub it will be colorless.
6. The only oil that becomes discolored over time is oil that has not been well cleansed of ts mucilage and the fine powdered husk seed components caused by the pressing.....both...the mucilage and the very finest particulate are in complete suspension in the oil and neither will drop of their own. They must both be removed and mechanical filtration will not remove the mucilage but will remove the seed husk particulate. The old masters tried everything they had available o test...ashes...urine..powders..etc etc etc. the old recipes are sometimes laughable...a touch of this...a pinch of that (like your pinch of salt method) ..a piece of this and that..shake and swirl and bake and repeat endlessly....but the one ingredient that will remove the mucilage is ethanol. Ethanol is a component of drinking liquor. See my book for to formulas using liquor. Both are based on Francisco Pachecos method (he was Velazquez teacher) .
7. The reason your oil looks transparent when seen in the photo from above is due to the warmth of the day. Put that oil in the refrigerator and if it remains clear...then the mucilage is out. The mucilage in the oil is visible not in warm weather...but when the day or night gets causes the oil to become hazy, cloudy, turbid.
8. One other way to remove the mucilage s to STAND ...NOT SHAKE TOGETHER...stand the oil on water. Water is polar and it takes 30 to 60 days depending on quantity of have the mucilage drop down to the level of the water. This happens because water is POLAR acts like a magnet. But you met remove the lid from the jar and the water must be minimum twice the amount of the oil. The taller he jar the longer it takes...use a wide container for faster results and also expose t to the or indirect to begin the bleaching ( in storage the yellow will return but it is pale compared to fresh pressed oil)...and like I painting..the yellow is fugitive and disappears.
..kindest regards...Louis

Unknown said...
This comment has been removed by the author.