A word about mediums
by Larry The Painter
To make paint, you add color to glue. In rare instances, the color IS the glue. For a minute, though, let's talk only of the glues.
The glues will come in 3 basic types, indentified by the type of material that will "thin" it or clean it up. These materials are Water, Mineral Spirits, and a very broad category called Alcohols.
The alcohol-based glues (called Mediums) are generally special-purpose products, meant to seal, or be resistant to strong chemical environments. Shellacs and lacquers fit into this category. Alchohol-based mediums are generally hard to tint, and unless you are highly experienced, you might think about leaving these poisonous and difficult-to-use coatings for later.
The mediums that will clean up with Mineral Spirits are the seed oils, like flax/linseed, soy, and a synthetic (man-made) product called Alkyd Resin. The varnishes also belong to this family, as they are refined tree sap. The "spirits" base paints have their own set of controls, and will readily accept tints. They almost always set and cure smoother and harder than the water bases. It was thought they were more durable, but history is showing us that is not necessarily the case.
The mediums that clean up with water have a bunch of fancy names, like acrylics, latexes, and urethanes. Again, one must use controls (additives) suited for this medium. Acrylics are among the easiest to tint, dry quickly, and in most cases have better resistance to sun fading than other mediums. They are non-toxic, easy to handle, and less expensive than the other 2 mediums.
There IS a common denominator but stores are taking it off the shelves so they can sell their higher-priced "special" additive. The one material that will readily enter a mix with all three of the mediums is glycerine. Pure glycol is the same thing as glycerine, and for now you can still get glycerine suppositories at the drug store that will work just fine. Use this material to make glazes, as a base for your colorant, and to control the behavior of your coatings.
You may email me through this site with specific questions. Have fun and don't drink the paint.