I just started oil painting and Im wondering about how you guys mix and what you use to mix your oil colors with thinner and mediums. And could you also break down how the layering system works, I get but kind of not.
An appropriate painting medium is composed of both a drying oil, such as Linseed, AND a solvent, such as Turpentine, or Odorless Mineral Spirits.
Either one used alone as a "medium" is not to be recommended. Oil, when used alone, creates an extremely long drying time, while Odorless Mineral Spirits (solvent) causes the paint to become "underbound"--a condition in which the particles of pigment become washed free of their Linseed Oil binder. When a paint is underbound, it will chalk off on your hand, even after it has dried.
Those of us who do a lot of layering and glazing also add a bit of resin to our medium. I use Venice Turpentine for that purpose. It is a balsam--the sap of a Larch Tree. A resin helps to create better adhesion between the dried underpainted surface, and the fresh paint as it is being applied. The resin helps to discourage beading, which often occurs during the application of fresh paint to a hard, shiny surface, such as the underpainting.
"Gossamer"...16" x 20"..oil on Linen RayMar Panel.
This is an example of a painting that I began with a totally gray (grisaille) underpainting, and glazed many thin layer of colors of paint over it.
I use the following recipe for my most personal glazing/layering painting medium:
1 portion Linseed Oil
1 portion Walnut Oil
1 portion Venice Turpentine (the RESIN in this recipe)
2 portions Oil Of Spike Lavender (the SOLVENT in this recipe)
To use this medium I spread it out very thinly upon the surface of my dried underpainting--so thinly that it only shows a slight sheen, compared to the surrounding, untreated areas. I then apply full-bodied paint into this very thin application of medium, using the medium as a lubricant for the paint application, rather than as a "thinner", or a "diluent" for the paint.
That is glazing, at its best.