Went to my sil last night to make potato bags had 100% cotton material and batting. Put our first ones together piece of cake they're so easy. Then I said I wonder if our thread had to be 100% cotton. So down to the kitchen we went. Threw hers! in the microwave. TaDa fire. Now the problem could have been the 1 thread 2 her microwave is as old as can be first ones made. 3 no turntable 4 no potato with wet papertowel. So after we fanned the kitchen out put out the fire in the bag. I went upstairs took my bag completely apart. Now off to the store to find cotton thread. Does anyone make these for craft shows went to the one at EJ Thomas hall last week she was sellin a lot of them. Do you use 100 cottn thread