I just completed my first successful batch of hand refined linseed oil out of organic, cold-pressed Flaxseed oil. It is beautiful and I'm over the moon excited to make some paint and test it out to learn it's unique properties.
I also have half of my new oil thickening in the sun, I plan to use that bodied oil for my hand made calcite putty medium. I've learned that combining calcite with lead white creates Ceruse or 'lootwit' and was used by Rembrandt and Velazquez for translucent passages. I also purchased some barite, after learning it is even more transparent than calcite and was used by the Old Masters with lead white as well, it was called Venice Ceruse, or Venetian white.
here is the good quality oil I purchased to cleanse and make into linseed oil:
I've combined the oil with water, salt and sand. A chemical reaction takes place and the mucilage and impurities are separated from the flax oil, they settle into the sand on the bottom, the cleansed oil floats above the salt water layer: ingenious!
After several mixes and changes in water/sand/salt I have the resulting oil, a bit cloudy from water particles still in the oil but cleansed of the mucilage, fatty acids (Omega 3s) and impurities that slow drying and yellow over time:
After setting in a glass tray in the sun for a few days to clear, we have the finished oil! My own batch of hand refined SRO (salt refined organic) linseed oil will now have its own unique personality compared to the commercial hot pressed, alkali-refined linseed oils. Commercial linseed is stripped of all the properties that create unique painterly effects. This is due to the fact that they are refined in the same manner as vegetable oils are refined for consumption. The qualities that are desirable in oil painting are stripped from the oil in the commercial process to create a long shelf life. Hand refined SRO oil keeps all the good stuff and eliminates the impurites and mucilage, resulting in an oil that the older painters prized in their hand made materials.
My oil will create long, adhesive paint as opposed to 'short and bouncy', it will not yellow and will dry much more quickly now and to a strong, hard film. These are exactly the characteristics I'm looking for in my painting practice. If I were to heat this fresh oil to 100C on my stove for an hour, the resulting oil would create paint that is short, bouncy and dense. My other half (that is thickening in the sun at the moment) will also have unique tendencies and rheology in my paints and mediums. I love learning all the different painting qualities I can create, and am in complete control over, by processing my own materials.