My kiln shelves are flaking apart and my question is, are they salvageable? And if so, how? They were bought second hand but lightly used, and I only fire them to cone 6, sometimes cone 7 as I have hot spots in my kiln. It just started happening after about 2 years of regular use (2-3x a month). It seems like there would be no way to get them flat again without grinding the whole shelf down, and it is happening on both sides. I'd really prefer not to buy new shelves...