Kemper Tools KMSPG Clay & Pottery Sculpture - Sponge Holder Kemper Sponge Holder gets way down inside without gouging. The special hardware attaching the sponge protects your piece and can easily hold your favorite sponge in place.. This Sponge Holder made of hardwood wont bend or flex under stress.. The tool is 14 in. in length.. The ceramic sponge is included attached by special hardware that will firmly hold any sponge.