I’ve written about my everyday-medium plenty of times. I frequently modify my medium for certain situations. Sometimes, for example, I add a little Venice turpentine to the regular turpentine I use in my medium. I add a very small amount of the sticky Venice turpentine to the medium.
Other times, I add a small amount of sun-thickened linseed oil to the medium. In this photo, the smidge on the end of my palette knife is all I add to my medium. The medium cup contains my usual three-quarters TBSP of medium. This small amount brightens the paint and makes it more covering. I use it in the lights; not the darks. Just this small amount has a dramatic effect.
I don’t use stand oil. Some writers confuse sun-thickened oil with stand oil but their handling properties are very different. Stand oil is produced by heating the oil to a high temperature in a vacuum. Stand oil is runny, like honey; it levels paint. Sun-thickened oil is sticky, somewhat like Venice turpentine, and holds a stroke. Sun-thickened oil is made by placing oil in the sun for 2-3 months. Times vary depending on the season and climate.
The jar in the above photo was purchased from Robert Doak some years back. Like everything else I’ve bought from Doak, their sun-thickened is really good (their vermilion red is excellent). But I hate trying to deal with them, so I am making my own sun-thickened oil.
In this photo, the jar on the windowsill contains cold-pressed linseed oil. I’m going to leave it there until it thickens. To do it properly, I should put the oil in a flat container, such as a baking pan. But this simple way will work even if slowly.