Question: I use only half shelves. I'm loaded in preparation for a Long Bisque load, but before I start the kiln on Wednesday night, I want to know whether or not it is okay to use kiln cloth in the firing chamber. Two half shelves are not exactly even at the seam and I have a vessel sink to fire. I solved the slight unevenness by using scraps of kiln cloth (don't know what else it's called*) on the shelf to place the sink on. It seems very stable now, but since then I have not used more than just a wad of the "fabric" inside a kiln before, and not inside my nice, new electronic L&L. The kiln cloth is the material used to line the inside of a raku kiln, I think. A previous teacher gave me a sheet of it to place between the bottom of an old kiln I acquired once and the base it sits on. The pieces I used to put the vessel sink on are the triangular trimmings from that sheet.
Answer: "Kiln Cloth" is not a technical name that one can be certain of. Here is how to think about this: Have you used this material in the kiln at the temperatures that you are about to go to?
It is probably some sort of ceramic fiber material. There are various grades of this - all of which go to typical bisque temperatures (1800 Deg F or so). Probably the worst that could happen is that it may disintegrate at a high temperature and lose any structural integrity which could pose a problem for the stability of your load. That ASSUMES it is ceramic fiber. However, what if it is fiberglass? Then it will melt and be a whole lot worse. Be certain this material can take your bisque temperature.