Use this medium for the earliest layers of a painting. It is almost pure solvent, with just enough oil mixed back in to make up for the binder that the gesso absorbs from the paint.
Working in multiple layers? Stick with this recipe for the first session only, then move on to Painting Medium #2. Painting alla prima instead? Switch to Medium #2 as soon as the surface is fully covered and the paint no longer feels tacky.
How much oil you need depends on how oily your paints are and how absorbent your ground is. Use the drying speed slider to compensate: turning it down adds a bit more oil, which suits a more absorbent gesso.
Properties
Ingredients
Use gum turpentine as the solvent. Odorless mineral spirits are a fine substitute if the smell bothers you, but turpentine is the better solvent overall: it is stronger, evaporates faster, and does not leave behind the mineral residue that spirits can.
Any fast-drying oil works here. Refined oils dry faster than raw ones, and alkyd oils are a good option too since they set quickly. Avoid slow dryers such as walnut or safflower oil at this stage.
How to prepare
There is not much to it: weigh out the ingredients and mix them well. Since you will likely fine-tune this recipe to your own paints and studio conditions, measuring by volume works fine too. Store the mixture tightly sealed in a cool, dark place.