Knife sharpening hack

Just about every ceramic cup/bowl that I have has a ring of unglazed area underneath. This is where the thing contacts the kiln while the glaze is being fired. The unglazed area makes an excellent sharpening stone/hone. It’s the same idea as a ceramic steel. It feels a lot more abrasive than the metal steel I have so I only resort to this honing if I feel I need more honing than the metal steel provides.