Good mortar and pestle-making materials must be hard enough to crush the substance rather than be worn away by it. They cannot be too brittle either, or they will break during the pounding and grinding. The material should also be cohesive so that small bits of the mortar or pestle do not mix in with the ingredients. Smooth and non-porous materials are chosen that will not absorb or trap the substances being ground.
Women in Cape Verde use a large mortar with multiple pestles
In food preparation, a rough or absorbent material may cause the strong flavor of a past ingredient to be tasted in food prepared later. Also, the food particles left in the mortar and on the pestle may support the growth of microorganisms. When dealing with medications, the previously prepared drugs may interact or mix, contaminating the currently used ingredients.
