Using Oil Paint Mediums
When painting with oils, there are many different types of mediums to help you achieve different looks. Mediums can do one (or more) of six things: make the paint thin or thick, gloss or matte, or dry quick or slow. Depending on your painting style, or the needs for a specific work, you can find a medium that best suits the situation. Thinners such as odorless mineral spirits are considered thin, and oils are considered to be fat. You have to be careful not to be too far right or left on the spectrum, because the chemical composition of the paint could change. Gamblin is great resource for learning about oil mediums: