Expert: Tom Riddolls M.A.C. - 2/13/2011

Question
I have a client who was bringing me three oil paintings to be cleaned.  He left them in a vehicle overnight in freezing weather.  There is some cracking in the paint in a small area, only in the white area of some clouds in the painting.  
My question is, do you think the cold temperature could have caused the cracking?  These are very fine line cracks and only in the white area as I said before, and only in the one painting.  I am sorry I do not have a photo to send but do appreciate your opinion on this.

Answer
Sudden changes in temperature can certainly cause localized cracking.  This is very common in younger paint films as the softer less cured paints can still shift around quite a bit with changes in temp.  However, with very old oil films that are 100+ and therefore already brittle cracking can occur when the paint film is cold and is subsequently impacted (jarred, bent, buffeted by wind) due to a huge increase in the brittleness of the film.

That said what you describe sounds to me more like common drying cracks as it is characteristic of just one area of paint.