Understanding Fat Over Lean

When it comes to oil painting, you’ve heard the term fat over lean. But what does it mean exactly?

Mary Weisneberger (Ep.53) from Gamblin says that the answer has nothing to do with the thickness of your paint.

Oil paint is made of, well, oil. This is considered fat.

Oil paint straight out of the tube is very fat because it’s basically a combination of pigment and oil.

However, if you add a bunch of solvent to your oil paint, that solvent breaks down the particles and makes it less fat. It makes it lean.

Put it to Practice:

If you’re working alla prima (also known as wet into wet), then you don’t have to worry about fat over lean.

But if you’re letting layers of paint dry in between, you want to make sure you’re working fat over lean.

Here’s how you do that. You want to make sure that the first layers you put down are your thinnest (more solvent in your mixture) and that later layers are fatter (less solvent more oil in your mixtures.)

For example, you’d paint your underlayer with an oil + solvent mixture, let that dry and then paint on top of that with straight oil paint.

Fat over lean isn’t about the thickness of the paint. It is about the amount of oil in the paint.