Share 'large platters'

i wanted to ask all on this who make large platters how they are wadding their platters? I have been making and firing large platters for a long time, but recently it seems the platters are shrinking off the wadding. It's as though the wadding is not moving with the platter. The result is serious warping, both porcelain and stoneware. Has anyone ever put down a thin layer of alumina to help the w…