I have read WAAAY to many accounts of these "microwave save" quilting products catching fire in a microwave.
https://www.google.com/#q=microwave+...ags+catch+fire
Here is an account right here on the QB
http://www.quiltingboard.com/main-f1...-t77011-3.html
Personally I would not risk ever making any microwave safe fabric bowl, potato bag or anything fabric that is going to be "nuked" for more than just a few seconds to a minute. Any longer is just asking for trouble. If you are dead set on making these microwave fabric bowls, I would use a 100% cotton with NO SCRIM (such as Mountain Mist products) and include a note to not microwave bowl for more than one or two minutes. But really, how would you feel if your bowls that you gifted to your friends, caught fire in the microwave? Why take the risk?