We can use mediums to change the handling properties of our paint, thinner, thicker, syrupy, stringy, fast or slow drying, etc. There are just short of a million little bottles of various mediums in the supply stores. As with anything you buy, don’t believe the marketing hype. I have used them all and, believe me, if you learn to use these two very simple homemade mediums, you’ll be alright.
Side note: medium is also a word we use to describe the materials we’re used to make an artwork, “oil on canvas” or “watercolor”, for example. Different usage of the same word.
In this class, using oil paint, we’ll be making two mediums. One is thin and the other thick.
Thin medium
Stand Oil (partially polymerized linseed oil) and Solvent (Gamsol) – more or less equal parts. The medium dries in two ways, first by evaporation of the solvent (like the water in watercolor), and then by the continued polymerization of the linseed oil, forming a tough film that can’t be redissolved. In the drawing or underpainting layer, you can use more solvent – as much as 70% solvent to 30% oil, making the paint leaner and quicker to dry. You can also add a drop or two of a liquid drier (a chemical catalyst) to your medium cup to accelerate drying. Cobalt drier is common, but CoZiCa and Courtrai Siccative are even more effective.
Thick medium
Calcium carbonate (precipitated) and refined linseed oil. Link to recipe.