 What is art resin's heat resistance? The maximum temperature that you should keep your art resin at is a hundred and twenty degrees Fahrenheit or fifty degrees Celsius. At those temperatures, the cured pieces will actually be a little bit flexible, but once they cool off, they will be nice and stiff again. If you heat your pieces even more than that, like let's say you leave your piece in a hot car for a long time, it could cause irreparable damage. So word of the wise, keep it cool.