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Question asked 2019-08-06 20:33:10 ...
Most recent comment 2019-08-08 02:14:39
when doing indirect oil painting how long should you wait before you apply the next layer? (using paste paint straight from the tube, unaltered in any way). From my understanding of artists comments it would seem commonplace for them to e.g. start a painting in the morning; then have a lunch break, then return to the painting to add further layers in the afternoon. I have also heard that some artists will overpaint the following day(s) because the iniitial painting is still wet. Stating that this slow drying was one of the advantages of oil paint in that you could continue to work on the same painting day-after-day.
From one of the articles on this forum it discusses how oil paints dry through a process of oxidative polymerization i.e. oxygen permeates the oil paint and starts the long, slow process of cross-linking of the binder molecules until a solid eventuates. Subsequent layers slow the ingress of oxygen down into the underlying layers but don't stop it. This process is faster at the start, then slows down apparently.
If I was to apply additional paint to a partially dried layer does this have any detrimental effect on the polymerization of underlying layers? For example, in the case stated above where I return to a partially dried painting the same day, or the following day(s), will I do permanent damage? Or will it have no negative effect on the painting as a whole? It seems such a common practice.
I realize that enviromental factors come into play in that in hotter weather the paint will dry faster than in mid-winter. But I have never heard this being a factor in relation to the above scenario.
Another reason for my question is that in our summer time it can get really hot, well into the 30 degrees ,or higher, and the paint will start to tack up a little bit even after just a couple of hours. Should I stop then and let it go touch-dry, or OK to keep painting?
Appreciate your advice
Answers and Comments
There is no issue painting into a still fluid paint layer
with additional paint, period. Painting over paint that has barely set is
probably a poor idea as is explained below. However, much of what you imply is also
true. Oil paint will continue to oxidize under layers of superimposed overpaint,
albeit in a slower manner. If care is taken to allow the initial layers to dry
to at least a minimal degree (generally taken to be able to withstand a
fingernail test ad leave no mark) there is likely not going to be a problem. I
know that you want exact numbers here but it is impossible to do so. It is
contingent on paint thickness, environment, and very important, what pigments
are present. Real problems occur when lower layers are still mobile and more
plastic and remain so because of the slowed rate of oxidation. In a scenario
like this, the uppermost paint layers will become brittle before the lower
layers become rigid. Cracking is inevitable in this situation.
I wouldn't hesitate to resume work in oils same day, after a lunch break. Where partially dry paint is concerned, however, in addition to the likely paint failures explained by Brian, personally I find it to be an utterly miserable experience, pushing around fresh paint over sticky or skinned-over work from a previous day.
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