On making potato microwave bag: Use ONLY cotton materials and thread throughout the project. We learned of some fires from using these bags (while I was working for a fabric outlet) and the answer seemed to be is not to use any chemically based materials (polyester, acrylic) in the construction. I wish I knew whether Insulbright is safe to use. These bags are longer than wide, about 10 x 15, fully lined, with batting inside. I quilted mine around the design of the outside print, then finished the bag with a turndown of the top. Flannel is good, at least for the lining.