Sanding Clay Use Wet/Dry sandpapers which can be used with water. Sanding sponges and sanding films with plastic backing are also available. Some brands of emery boards are similar to sandpaper. When wet sanding baked polymer clay, add a little dish detergent to the water. Choose a scent you really like. It will make the water more slippery to ease your sanding. Sandpaper comes in numbered grits, with lower numbers being coarser than high numbers. The numbers correspond with number and size of grit per square inch. 150 grit - very coarse, cuts through and removes a lot of clay very quickly 220 grit - removes lots of clay 320 grit - removes clay 400 grit - approximately the same grit as polymer clay - removes some clay 600 grit - polishes clay surface 1000-2000 grit - found in auto supply stores, polishes clay to a very smooth surface. Hint - The surface of ordinary brown grocery bags is similar to 400 grit sandpaper. Start with as coarse a grit as you need and water, then use progressively finer sandpapers until you achieve the desired surface. Each grit of sandpaper removes scratches from the previous coarser grit. Most of the time 600 grit is high enough unless you want an absolutely silky finish. Keep your piece and your sandpaper wet and rinse frequently with clean water. Sand in a circular motion - do not always sand in the same direction. Remove sanding sludge from any crevices before re-baking or it will bake into the clay permanently. Faster sanding is possible by partially baking your piece at 210-220 degrees for 15 minutes, then sanding. Support your piece very carefully since partially baked clay is soft and fragile. 400 grit sandpaper cuts partially baked clay like 320 grit cuts fully cured clay. Sand up to 600 grit, make sure all sludge is removed, and rebake for the normal time and temperature. Baking will remove sanding marks. A light sanding can be done after baking.