Each Monday in the summer I show and sell my work on a Village Green with a group of artists. In the last year, many trees have been taken down, so artists who were in the shade are now in direct sun all day. I am an oil painter and am wondering if all that hot sun can hurt my paintings. Does direct sun degrade oil paint?
I think if you use only pigments that are lightfast, you should not have a problem. Most brands rate pigments with a code on their tubes ranking them. You don’t say where you are, but if the temperature is very high, the paint may soften and hold an imprint if anything presses against it. Can you use an Easy-Up or umbrella to keep the sun off? When I used to paint plein air, I would use a big umbrella or a sun shelter made to cover a picnic table.
The brief exposure of a few hours in the market should not fade the colors or damage the paint. The heat on a hot day, or in a hot vehicle may soften the paint surface temporarily.
I would advise customers not to hang the paintings in direct sunlight. It is usually long term exposure that causes issues.
A canopy or sun umbrella would a kindness to the artist as well.