1. Pour a pot of boiling water onto the mortar and pestle.
  2. Add the desired amount of soap to the pot, and stir until the soap is melted. Pour the soap mixture over the top of the mortar and pestle, and stir until all of it is mixed in.
  3. Place the mortar and pestle in a warm place, such as a oven or stove, and let it sit for about 10 minutes so that all of the soap has melted down.
  4. Remove the mortar and pestle from its hot spot, and use a cloth or paper towel to clean it thoroughly. Be sure to dry it off before putting it back into use!