I tend to put a thin coat of some colour just before painting. It seems to help with the later layers of paint. But I am never really sure what colour to choose or whether I should just tone the gesso so the tone colour does not mix with the painting. Also if you are putting down a light sketch to find landmarks in your painting, what paint do you use for that and what is your rationale for making these choices? Are there some paint colours you would never use for toning a canvas or sketching.
At the risk of talking too much…
I usually tone my cavas or board with acrylic, because it dries fast and doesn’t mix in–though in figure painting sessions when I’m unprepared, I done a quick oil wash with terra rosa or burnt sienna thinned with Liquin (dries fast). The overall color of the painting somewhat determines the base color. Often I go with something complementary(ish). Sap green and terra rosa make a nice sienna(ish) undertone for outdoor scenes. Sometimes I go with a grey(ish) neutral, sometimes something brighter, usually in the orange-red range, but occasionally green or purple. It helps me psychologically to work on a middle value, but the exact color usually doesn’t matter much, because I end up completely covering it. The only under-tone I personally probably wouldn’t use is blue. I sketch with something in the brown/red range.
In oil painting, you want to keep things as simple as possible.
Remember there are only 3 rules to keep your painting in the best possible shape for a long time:
- Fat over Lean
- Thick over thin
- Slow drying over fast drying
An oil wash basically ignores the fat over lean rule.
I personally use a bit of White Spirit (similar to turps) on my first layer to wash and/or sketching the basic composition.
Painting wet in wet, I am forced to calculate the effects my ground colour will have on my eventual painting.
I also use a small mirror to check my composition and proportions throughout the first stages of a painting.
Advantage: all colors are bound together and there is more chance of unity in the overall composition.
Sometimes I use just a little bit of White Spirit on the 2nd layer -in any case less than on the first layer (= rule nr 2), but from the 3rd pass on I use paint only (rule nr 3).
If you want to start off with a toned ground but do not want it to mix with your 2nd layer, I strongly advise you to prepare your carrier with the desired tone at least a day up front so it is dry before you start. Use just enough paint with turps to make it dry faster.
Be careful with the phthalo colors, they are very strong pigments and are harder to control when painting wet in wet.
I have tried and really like Gamblin’s Fast Matte line, which are designed to use as an under painting for oils.
Otherwise I usually use a thinned earth color. I like to use a red leaning color like Terra Rosa or something similar if there will be a lot of greens.
Yellow ochre is also one of my favorites for western landscapes.
I prefer to use turpentine for toning the board. Usually with a little Transparent Oxide Red, and Viridian (makes a great grey) depending on how warm or cool you want it. The turpentine dries very quickly and I can paint right over it with very little getting picked up by the next layer.