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Free Art Tutorials: What Is Fat Over Lean?

By Milan Art Institute on June 25, 2021

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Photo caption: Milan Art Institute co-founder and instructor Dimitra Milan shows off a painting done with the fat over lean technique. Photo courtesy of Dimitra Milan.

The technique of painting fat over lean has also been called a rule when painting in oils. As creatives, we don’t always like to follow rules. We want to break free; to think outside the box; to burst through the boundaries, etc. That’s how we change the world, right?

Yet, there are times when rules are needed. Understanding them and the Why behind the What, actually helps us become better painters and essentially, better people. So, let’s start with learning the What.

What Is the Difference Between Fat and Lean Paints?

Fat Paint—Paint with higher oil content.

Lean Paint—Paint with lower oil content.

Notice that it does NOT refer to a thin layer or thick layer of paint.

Oil paints are a mixture of oil (generally, linseed oil), pigment, and sometimes added fillers. The ratio of oil vs. pigment, solvent, etc. is what determines whether it’s lean or fat. Depending on the medium you use, you can make any paint various grades of lean and fat.

Mediums To Create Lean Paint

Alkyd is a synthetic resin and treated with alcohols and acids resulting in quicker drying times. When adding these mediums to your oil paint, you will still have many of the benefits of oil paint but it will generally be touch dry within 24 hours.

Copal mediums are made of natural resin. They not only add speed to the drying time, but also give your paint a brilliant enamel-like glaze finish. Lighter colors retain their brightness and darker colors become more vibrant when mixed with copal mediums. However, another rule applies here—less is more. If too much of this medium is used, you may see a yellowing of your colors.

Mediums To Create Fat Paint

Cold-pressed linseed oil or stand oil are mediums used to create glossy finishes that are very slow in drying time. Cold wax will create a matte finish while also drying slowly. Damar varnishes create a smooth glossy finish (notice the word finish - it’s a very fat medium and is the last thing added to your paintings).

Trying to figure out the various mediums can be overwhelming. Chelsea Classical Studio mediums make it very simple. They have both a lean medium and fat medium (amongst others), which makes it quick and easy to get the effect you seek. The lean medium is made of linseed oil and spike lavender oil. The fat medium is the same as the lean with the addition of damar resin.

Why Should Artists Paint Fat Over Lead?

The Why is all about the drying time and how it affects your painting. Remember, it’s about the oil content in the paint, NOT the thickness of the paint.

OK, so here’s where we get a bit technical.

Oil paint oxidizes and hardens as it dries.
With weather changes, it can expand or contract.
Lean oil paint dries and hardens more quickly than fat paint.

With those principles in mind, picture this: You’ve started your painting with a juicy, rich layer of fat paint. You let it dry (well, at least to touch dry) and then begin a quick thin layer of lean paint. Your beautifully rich underlayer now has a film over it creating a matte look. Not only that. But since the lean layer dries and hardens more quickly, as the fat layer underneath contracts and expands, the thinner layer on top may crack or even flake off.

That’s the Why to this rule. If you want beautiful, archival quality paintings, you will need to follow the fat OVER lean rule.

Who Uses This Technique?

Dimitra Milan, co-owner of Milan Art, has been using the fat over lean technique in her amazing paintings. She often begins with a sketch and mark making. She adds inks and acrylics providing the first lean layer.

As she builds, each layer becomes fatter, even adding cold wax to add dimension. Once the painting has cured, she adds a final glossy varnish that punches up the colors and brilliance of her artwork.

If you’d like to learn more about the fat over lean technique, sign up for the Mastery Program, over professional-level certificate program. Or go to our store to stock up on oil paints.