Mortar and pestle
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A mortar and pestle is a two-piece lab equipment, commonly used to prepare various powders or substances by crushing and grinding them into a fine paste or powder. It consists of two main pieces: the mortar and the pestle.
Another less common term used is mortar grinding machine.
The mortar and pestle is a very cheap and convenient method of grinding solids with low hardness. Common construction materials include commercial porcelain, sintered alumina, granite, glass, agate. Metal mortar and pestles exist, but are less often used, as they erode easy if used to grind materials that are too hard. Stainless steel mortars and pestles are more often used for grinding soft materials, like chalk, drugs and solid organic compounds. Exotic mortars made of very hard materials, such as boron carbide, sapphire or tungsten carbide exist, though they're very expensive.
The mortar and pestle consists of:
- Mortar: Has the appearance of a thick bowl, slightly curved. Kitchen mortars have a more cup-like shape and some have a foot, similar to glasses.
- Pestle: It has a baton-like shape, though shorter. Other models appear as a flat headed "lollipop".
The desired solid material is added in the mortar. In general, you should not fill the mortar more than 1/10 of its volume, as this limits the grinding. To grind the material, take the pestle and press against the material inside the mortar, either in a circular or up and down motion. After grinding, shake the mixture to break up the compact powdered material and repeat. To obtain a very fine material, use a sieve to separate the finely ground material, add it back in the mortar and repeat the procedure.
Materials that are brittle are the easiest to grind, with powders being relative difficult as they tend to stick, while materials that display cleavage, like diatomaceous earth are notoriously hard to grind into a powder.
Mortar and pestles can be cheaply bought from hardware stores. Most tend to be made or granite or porcelain.
Lab mortar and pestles can be bought from lab suppliers, or online. Agate ones tend to be expensive, but they have good performance. Sapphire and carbide ones are very expensive, but being very hard are difficult to scratch and there's less chance of contaminating the grinding material.
- Grind stuff
Grinding sensitive energetic materials in a mortar is a bad idea and it's best to avoid doing that all together.