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.

In food preparation, a rough or absorbent material may cause the strong flavour 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.

Rough ceramic mortar and pestle sets can be used to reduce substances to very fine powders, but stain easily and are brittle.
Porcelain mortars are sometimes conditioned for use by grinding some sand to give them a rougher surface which helps to reduce the particle size.
Glass mortars and pestles are fragile, but stain-resistant and suitable for use with liquids.
However, they do not grind as finely as the ceramic type.

Other materials used include stone, often marble or agate, wood (highly absorbent), bamboo, iron, steel, brass, and basalt.
Mortar and pestle sets made from the wood of old grape vines have proved reliable for grinding salt and pepper at the dinner table.
Uncooked rice is sometimes ground in mortars to clean them.
This process must be repeated until the rice comes out completely white.
Some stones, such as molcajete, need to be seasoned first before use.
Metal mortars are kept lightly oiled.
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.
In food preparation, a rough or absorbent material may cause the strong flavour 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.
Rough ceramic mortar and pestle sets can be used to reduce substances to very fine powders, but stain easily and are brittle. Porcelain mortars are sometimes conditioned for use by grinding some sand to give them a rougher surface which helps to reduce the particle size. Glass mortars and pestles are fragile, but stain-resistant and suitable for use with liquids. However, they do not grind as finely as the ceramic type.
Other materials used include stone, often marble or agate, wood (highly absorbent), bamboo, iron, steel, brass, and basalt. Mortar and pestle sets made from the wood of old grape vines have proved reliable for grinding salt and pepper at the dinner table. Uncooked rice is sometimes ground in mortars to clean them. This process must be repeated until the rice comes out completely white. Some stones, such as molcajete, need to be seasoned first before use. Metal mortars are kept lightly oiled.
Mortar and pestle