… a la Tad Spurgeon. Thanks to Mr Spurgeon for his research and resurrecting such a valuable technique!
This post assumes some knowledge of Tad’s research into how painters in the past may have treated their linseed oil before painting with it. And this post shows my first batch following some of the proceedures out-lined on Tad Spurgeon’s site.
The purpose here is not to re-present what Tad already does a good job of explaining, but to demonstrate that the purification of organic cold pressed linseed oil for use in painting can be performed in an urban situation as long as there is a window on a sunny side.
The picture below indicates why re-learning the techniques for purifying linseed oil is important for the oil painter. Below are two bottles of the same brand of store-bought linseed oil. But the bottle on the right is 15 years old.
This store bought linseed oil has not been subject to the process Tad oulines : salt/sand ethanol/water purification procedures. Instead, most likely it has been subject to the faster industrial methods of the 20th century, with its zeitgeist for reinvention. Proceedures that modern linseed oil for painting is subject to includes boiling, treating with metals to prevent rancidity, and chemical bleaches to make the oil lighter (for a while). The bottle on the right is only 15 years old and shows considerable darkening, which would be bad for a painting, particularly for the whites, yellows, and transparent glazes.
If we are concerned with archival standards, we do not want to paint with cheap art store linseed oil, but pursue the best quality possible for the fundamental ingredient in our painting. Which would not be the art store stuff bought below which has aged and darkened horribly within a ten year period.
Below you can see my sunny windowsill in an urban apartment situation with 3 mason jars receiving about 7 hours sun a day on a clear day in England. This is the oil directly after 3 rounds of flushing through with salt water, ethanol, and clear spring water. Each flush took one week, the layers separated with a turkey baster.
The following photograph shows the conclusion to the process and an indication of why such a procedure would be pursued: the result being a fast drying linseed oil which has not been ‘denatured’, which is much cheaper than store bought & of much higher quality (organic, untreated with metals or bleaches). This oil does not darken to anything of the extent of store-bought, and produces a hard yet flexible film because emulsive gums and waxes have been removed by salt, ethanol and water cleaning.
All three jars received the same light. The jar on the left had breathable muslin gauze so received the most air as it was sun-bleaching. The second jar had a silk gauze, so could still slowly absorb air from the environment. The third jar was sealed. As we see the third jar bleached a lot less, so obviously air is important to the bleaching process, not just sunlight.
The leftmost, lightest oil dries the fastest. Surprisingly, it dries within a few days if used lean (and combined with gum turps and resin in a medium, with the faster drying pigments it dries overnight). It also has the most ‘grip’. This is the goal of the process, successfully achieved in an urban environment without garden.
The second jar of oil received the same light but the silk prevented it receiving as much air. The oil is slower drying, has less grip, requires more pigment to avoid beading.
The third oil handles almost the same as when I put it in the jar, it is too ‘slippery’ and very slow drying, and when it does dry, the film has a slightly ‘jellylike’ or rubbery surface that repels subsequent layers unless subject to abrasion via very fine sand paper.
The satisfaction of using ones own SRO linseed oil (salt refined organic) is great and I recommend this process (and Tad Spurgeon’s website and book) to anyone who likes traditional techniques and likes to be intimately acquainted with their materials.