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Further Adventures in Bad Salad Dressing

Post #1837 • June 25, 2019, 5:21 PM

Having returned from the digital realm, I'm back to thinking about oils. On the way to the studio, I want to compile some observations regarding the experiments I began here.

This Pacheco Guy Isn't All He's Cracked Up To Be

You may recall from the post linked above that I tracked down a recipe for refining painting oil that was recorded by Pacheco.

Here we will treat how to purify linseed oil and remove its yellowness so that it will serve for white and blue. Take a glass flask and a pound of clean, clear linseed oil, three ounces of agua ardiente que llaman de cabeza, and throw in two ounces of lavender seeds. Put this in the sun for fifteen days and stir it twice every day, and it will become clear and purified. Strain it into another glass flask. Then it can be used to advantage in whites, blues, and flesh. More or less than the quantity of one pound of oil can be prepared, adjusting the amount of the other things in respect of what has been said.

For the untranslated Spanish, read "vodka." It was something like that. I was made aware of the Pacheco recipe through the work of one Louis Velazquez (no relation), who developed a method involving psyllium husks that he derived from Pacheco. Velazquez does not divulge his method. However, he does mention that

To test Eastlake’s method, place a jar of oil cleansed by his method in a refrigerator overnight at 40 degrees Fahrenheit. If the oil is truly cleansed of mucilage, it will remain fully transparent no matter how long it remains in the refrigerator. DO NOT judge oil cleanliness when the oil is at room temperature. Even oils full of mucilage are fully transparent at room temperature. But, oil containing mucilage becomes cloudy in the coldness of the refrigerator.

In fact, it wasn't hard to deduce the Velazquez recipe once I had found Pacheco's. It was essentially the same procedure, with psyllium husks substituted for the lavender seeds, and double the alcohol, which is doing most of the heavy lifting here. So I tried them, and I'm sorry to report that both of them fail the Fridge Test. In fact, they cloud in a few hours.

Back to the Drawing Board

Tad Spurgeon's recipe with vodka and spring water works like a champ, and it starts with a 1:1 mix of ethanol and flax oil.

An equal volume of oil and forty percent (eighty proof) ethanol are placed in the jar, filling it one quarter to one third full. The jar is then shaken thoroughly. The mixture emulsifies readily. The jar is shaken repeatedly over the course of a day, the more shaking, the better. At the end of the day, an amount of spring or distilled water equal to at least twice the volume of the ethanol and oil mixture is added, and the jar is shaken again. The following morning, the water-ethanol mixture is an opaque white, the clear oil has risen to the top of the jar, and can be removed.

The 16:3 and 16:6 oil-to-ethanol ratios in Pacheco and Velazquez are not enough hooch to do the job, in my opinion. Lavender seeds, which I obtained from a seed company at considerable expense, are not at all absorbent. If there's spike oil in the medium once the lavender seeds have sat in alcohol for a couple of weeks, it may lend some pleasant working properties, but I tend to doubt it. And while there may be value in refining your own linseed oil, refining your own spike oil is kind of dumb. Leave that to someone who can manufacture it by the decaliter, buy a bottle at the art supply store, and get on with life.

The psyllium husks are indeed absorbent. But it was clear from my unsuccessful attempt to get the Velazquez recipe to pass the Fridge Test that if they were going to absorb the mucilage, they were going to do it on initial contact. Leaving them in solution for a couple of weeks caused them to break down, darkening the oil a little, releasing the mucilage, and forming an unpleasant porridge.

I did, however, find another way to get them to work. Stuff a cotton ball into a funnel, and place it over a jar. Pour four ounces (by volume) of whole psyllium husks into the funnel. Pour twelve ounces (again by volume) of flax oil on top of them. Let sit until the oil has dripped through completely, which will take about three hours. Put the filtered oil in the refrigerator for another three hours or even overnight. If it clouds, repeat the process, but I have not yet found it to be necessary. Condition further as desired.

Spurgeon says that the vodka recipe does not dry especially quickly. He favors a salt- and sand-refining process that, to be honest, sounds like sort of a nuisance. (That and several other methods are available in the book linked above, which I recommend highly.) The psyllium husk filter might result in a faster-drying oil, but I'd want to paint with them both for a year or two before I come to any conclusions about that. On the other hand, you lose more oil through the psyllium husk method than the vodka method, so you'll have to decide on the trade-offs as you see fit.


Adding a little chalk to the oil seems to help it along significantly. Linseed oil, as you know, dries by binding with oxygen. If you store it in a sealed jar and let it sit for a week, it will make a satisfying hiss and pop when you open it again as the vacuum releases. If you let it sit for three months, you will have to beat the lid into deformity in order to get that vacuum to let go. This is the voice of experience. Spurgeon writes that he had to puncture a lid once to get it open, and has read about containers imploding. My observations tell me that between jars of plain oil and jars of oil that have been shaken with chalk, the latter form that vacuum much more vigorously. I think that speaks well of the chalk. Not only do you get an alkaline buffer against linseed oil's natural acidity, the product appears to want to reach stasis more quickly. Again, only painting with it will tell for sure, so stay tuned.

In Summary

1. Remove the mucilage from organic, cold-pressed flaxseed oil using the Spurgeon Vodka Method or the Einspruch Psyllium Husk Method described above.

2. Place the cleared oil in the refrigerator for a few hours or longer. It should be as transparent as apple juice. If it clouds, start over.

3. Add one tablespoon of calcium carbonate per cup of oil and shake.

4. Replace the lid of the jar with cheesecloth held in place with a rubber band. Keep the lid in case you have to transport it.

5. The oil can be used immediately but will benefit from exposure to light and air. Leave on a sunny windowsill for weeks, months, or years. Give it a friendly swirl periodically.

6. Buy Tad Spurgeon's book. Maybe this should be Step #1.




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