I made potato bags, and had the burning problem as well. I thought maybe I had mistakenly used polyester thread or something, so I bought a new bag of Wrap and Zap. Interesting update on that product--it now has a warning to NOT microwave for more than 2 minutes at a time, or for more than 8 minutes total. In cooking potatoes, I'd routinely set the microwave for 6-8 minutes--not any more! Small bowls, likely used for reheating for only a minute or so, would probably be much safer.