Warm and Natural cotton batting and other cotton batting has scrim. Scrim is a very think poly layer and poly is what catches on fire in a high wattage microwave. If you microwave is around 800 watts it think the regular batting is fine. Put a piece of any batting you want to use for the bag in the microwave and test it for the length of baking several potatoes. I wrap my potatoes in a cotton feed sack towel if I use the microwave. Not as pretty but works fine.