I have tested the Minwax spray polyurethane finish with 450 degree casserole dishes right out of the oven. I couldn't find any damage. I have had three such trivets in service at our house now for over a year and they still look pretty good. Grime is more of a problem than finish erosion. I am guessing that the Watco would resist heat just as well but I don't know about constant washing.

The pattern in the picture above is just one of a series of patterns I derived from on line postings of traditional quilt squares.