A deep, curved bowl on a sturdy base and compatibly shaped pestle are used for grinding tiny, hard seeds, such as cumin and fennel, as well as garlic, anchovies and nuts. They can be made of white vitrified porcelain, heavyweight ceramic, tough unglazed porcelain, stone, wood, glass or marble. The end of the pestle and the inside bottom surface of the bowl should both be slightly rough for maximum friction.
Use a sturdy pestle and mortar to grind whole spices, or for the traditional method of making mayonnaise or pesto sauce. Work the pestle round and round against the sides and base of the mortar.