What prolonged exposure to high heat will do is soften the resin, whereas you could take your fingernail and make an indentation in the coating. Although, it's also very important that the resin be mixed accurately and cured fully. We've found that some users are mixing such small amounts that they do not realize that they are going off ratio. Mixing off ratio could cause the product not to cure fully or cure to cured specification. If users are mixing less than 1 fl. oz., we recommend mixing 1:1 by weight. Overall, we recommend avoiding prolonged exposure to temperatures beyond 130F.