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| These are the mediums I use most often. |
I'm often asked by my oil painting students what mediums to use, when to use them and how to use them. Frequently, I find students are confused about mediums in general. “What's this about 'fat over lean'?” “Maroger medium—isn't that some long-lost secret of the Old Masters?” “Why can't I just use paint thinner as a medium?” And so on.
Well, it's not that difficult. Here's everything you need to know about mediums.
Here's the first thing to know. It's best to use no medium at all. A good manufacturer of artist grade paint fine-tunes its product so it works perfectly, right out of the tube. I always prefer to use paint without adding anything that might negatively alter its working properties or archival quality.
Here's the second thing. Mediums possess no magic. Despite the mystique that once surrounded Maroger medium—the inventor, Jacques Maroger, claimed to have rediscovered a secret formula used by the Old Masters—mediums are simply chemical compounds designed to change the properties of paint in certain ways.
So, when should a medium be used? Here's my list:
- If the paint is too thick to work, I can add a medium to make it more workable.
- If the paint dries too slowly, I can add a medium to make it dry faster.
- If the paint dries too quickly, I can add a medium to make it dry more slowly.
- If the paint needs a gloss (or matte) finish, I can add a medium to make it more glossy (or more matte.)
- If an area of a painting needs to have transparent color glazed over it, I can use a glazing medium.
Although there are other situations when one might use a medium, these are the common ones.
Any medium should be used sparingly. Manufacturers often list the recommended percentage for a mixture. Gamblin, for example, recommends that their Solvent-Free Gel make up no more than 25% of the mixture. (That is 1:3, 1 part SFG and 3 parts paint.)
By the way, a medium is not simply paint thinner, like Gamsol. If you add too much thinner to the paint, you risk weakening the paint film. The paint will flake off over time. The only time I use Gamsol is to thin paint initially for my block-in. After that, I don't use it. Instead, I use pure paint or paint with a proper medium, which will maintain the integrity of the paint film.
Although there are many brands and varieties of mediums on the market, I basically use three, all from Gamblin:
- Solvent-Free Gel
- Galkyd Gel
- Cold Wax Medium
The first two (Solvent-Free Gel and Galkyd Gel) come in tubes. I like the tubes because, as a plein air painter, I can just squeeze out a dollop on my palette and not have to worry about it running all over the place. And I don't have to use those messy medium cups. (I long ago gave up cups with screw lids, as the lids seemed to get welded on after a couple of uses.)
The Solvent-Free Gel is jellied safflower oil with a little alkyd resin added to it to make it dry faster. The Galkyd Gel is similar but contains solvent and dries much more quickly. Both of these give a glossy finish to the paint film.
The Cold Wax Medium is something I use only in the studio. It contains beeswax with a little Gamsol and alkyd resin added to it to speed up drying time. It gives a matte finish to the paint, and it can be used thickly to create translucent depth in a painting. Also used as a final varnish, it can be buffed to the desired level of sheen, like shoe polish.
(For more information on these products from Gamblin: solvent-free painting mediums,
contemporary oil painting mediums.)
Finally, let me explain the concept of “fat over lean.” Fatty layers of paint—that is, paint with more oil or medium in it—dry so that they are flexible. Lean layers of paint—that is, paint that has been thinned with a solvent like Gamsol—dry more brittle. You want the more flexible layers on top of the more brittle layers to avoid any cracking of the final paint layer. If you reverse this, and put brittle (lean) on top of flexible (fat), the upper, brittle layer is prone to cracking as the lower layer flexes. (Cracking, as you might have guessed, is not desirable, unless you are trying to forge an Old Master.) So:
- Lean = paint with solvent
- Fat = pure paint
- Fattier = paint with medium
Medium is always considered “fat.”
Now, here's a secret. The “fat over lean” rule applies only to “indirect” painting, where one paints in layers over time. It doesn't matter at all with “direct” or “alla prima” or “au premier coup” painting, where the painting is created in one session.
And that's all you need to know about mediums for basic painting. There's much more to learn, of course, and I urge you to read more about mediums and then experiment. The Gamblin site has lots of information on this topic, as well as videos.
