Drying Times

In the past two posts I discussed “fat over lean” and “sinking in”. In both posts, drying has been a part of the discussion, but it wasn’t discussed directly. Today I’ll share my understanding of this often confusing topic.

Different pigments dry at different rates, naturally. This can be influenced with different additives, but in general, titanium white dries very slowly, earth tones dry much faster, cadmiums and artificial pigments are somewhere in between. There are two classes of additives that can influence this. One is something that will retard the autoxidation process, and the other is something that will speed up autoxidation. This is the mass gaining phase of the paint film formation.

The additives that speed up autoxidation, called “dryers”, usually also have side effects in the mass losing phase of paint film formation, where volatile compounds diffuse out of the film as it hardens. The additives that slow autoxidation typically only affect autoxidation.

So, how and when do we add these, and why? There are dryers that you can add directly to your paint, but this is not usually recommended unless you know what you’re doing. The risk is adding too much and destabilizing the paint film as it forms. There are also additives that slow autoxidation, and these are not likely to cause destabilization of the paint film as it forms, but adding too much may cause separation of the pigment from the suspension medium.

There are also “fast drying” mediums and “slow drying” mediums that already have these characteristics. Adding these mediums to your paints will influence the drying rates. If you are very careful, you can influence the drying rates such that all the pigments dry at the same rate, which can result in a more stable paint film. Adding medium potentially also allows for more uniform autoxidation as the medium creates an emulsion with the drying oil the paint is suspended in, creating channels for oxygen molecules to penetrate. But getting the ratios right for each pigment takes a lot of patience and experimentation, and may even vary from batch to batch of both paint and medium.

There are two paints on the market that have medium already added. One is by Schmincke and is a fast drying medium. The other is Geneva, which is a slow drying medium. These both have the benefits described above and free the artist from having to mix in medium during a painting, fussing to get the right texture, running out of a color and needing to do that over again, etc.

I personally use the Geneva paint. I prefer its slow drying quality, the fact that all of the colors dry at the same rate, and the pigment load is outstanding. If you prefer a fast drying time, especially if you work in layers (indirect method), the Schmincke paints may be something you would be interested in trying. (Note, I have no affiliation with Geneva Fine Art or Schmincke, but I did take a series of workshops with Mark Carder a number of years ago and I’m definitely a fan.)

If you are interested in adding something like cobalt dryer to speed drying time, or clove oil to slow it down, it’s generally recommended that you do so very carefully — like a drop at a time. Otherwise, consider one of the many fast drying or slow drying mediums available on the market, or make your own using one of the many recipes.

There is still a question about how much drying times matter when considering the final paint film. Does uneven drying have a higher risk of cracking? Does it matter if you paint direct / alla prima? I don’t know the answer to these questions. I do think that it’s very likely any oil paint will crack eventually anyway though, so I try to keep it simple and focus in painting instead of chemistry.

My next post is probably going to be about painting mediums. Then again, it could be about clouds.