I am experimenting with the maiolica watercolor decoration technics and decided to use white clay. Got Standards LF White 100 rated at 04-06. The mugs came out fine, and were great in the microwave the first use out of the kiln, but every time I've tried to heat up my tea in the microwave since then the handle gets so hot I can't touch it. Obviously I can't sell. Used Arbuckle firing temps and base glaze. Bisque to 04 - Glaze to 05. Is this problem normal? Is there a fix? The mugs are cut direct