From my collection one of the interesting mediums, I call it 2-3.
If the thickness of your oil paints are keeping you from spreading or blending them easily, you need some additional oil painting medium to mix in with the paint.
2 part Stand Oil (or sun thickned)
3 part Turpentine
Stand oil is so thick that the two liquids won’t want to combine right away—be prepared to wait a few days for it to completely mix.
If you’re wondering what to put it in, glass containers with a tight screw on cap work best.
If you get impatient, turn the container on its side or top every few hours to help the stand oil and turpentine mix together faster.
Once it’s all one liquid, I usually pour just a small amount into a container and dip into it with my brush whenever I’m mixing colors or working with thicker, more opaque paint. Make sure to keep the rest of the medium sealed up and it’ll last quite a while.
There are a few other benefits to using this medium as well. It’ll make your oil paint tougher and more durable—and it will keep the skin of your painting from cracking as it dries.
As far as drawbacks go, there’s only one: drying time.
Oil paintings take longer to dry when stand oil is involved, up to a week (or longer even) depending on your location’s humidity and temperature.
If waiting that long is out of the question, you can substitute sun-thickened linseed oil for the stand oil and gain a few days.
Just realize that using sun-thickened linseed oil in your medium may turn your lighter colors (like white) slightly yellow over time.