Laboratory Pestles & Mortars

A mortar that is too small makes grinding awkward and risks losing material over the rim; one that is too large makes it hard to concentrate grinding pressure on a small sample. For general laboratory and classroom use, a mid-sized set covers most tasks, with a larger set kept on hand for bulkier mineral or plant material grinding.

The grinding action of a mortar comes from its slightly rough, unglazed interior surface, which creates friction against the sample. A glazed mortar interior is smooth and will not grind effectively, so always check that the inside surface of both the mortar and the pestle head is unglazed before buying a set for grinding work.

Porcelain mortars handle most laboratory samples well, from soft plant tissue to moderately hard mineral chips. For very hard or abrasive materials such as ores and rock samples, an agate mortar resists wear better over repeated heavy use, though porcelain remains the standard, cost-effective choice for routine lab and classroom grinding.

Porous unglazed porcelain can retain trace residue in its surface texture, so rinse and dry mortars and pestles thoroughly between different samples to avoid cross-contamination. For samples containing oils, pigments, or strong-smelling compounds, a dedicated set reserved for that material type avoids any risk of carryover into later work.

Unglazed porcelain has a naturally rough, slightly abrasive surface at a microscopic level, which grips and shears solid particles as the pestle moves against them. Glass and plastic mortars are much smoother, so they slide over a sample rather than grinding it effectively. This is why laboratory and pharmacy mortars are almost always unglazed ceramic rather than glass or plastic.

Porcelain is chemically inert and resists most laboratory acids, alkalis, and organic solvents at room temperature, making it safe for general chemical grinding work. Avoid prolonged exposure to concentrated hydrofluoric acid, which etches ceramic glazes and surfaces over time. For routine grinding of solids before dissolving in a solvent, porcelain is the standard, reliable choice.

Rinse with water immediately after use to remove loose residue, then scrub gently with a soft brush; avoid harsh detergents that can leave a residue in the porous unglazed surface. For oily or pigmented samples, a small amount of coarse salt or sand ground dry in the mortar helps lift stubborn residue before the final rinse. Always dry fully before storing.

A mid-sized mortar, roughly large enough to comfortably hold a golf-ball sized sample with room to grind, suits most school chemistry and biology practicals. Buying several of the same size makes it easy to equip a full class of student groups, and keeps replacement parts interchangeable if a pestle or mortar is ever chipped or lost.

Porcelain is hard but brittle, so a mortar can chip if struck against a hard surface or if very hard, sharp-edged rock or metal fragments are ground with excessive force. Grind with steady, controlled pressure rather than heavy pounding, and inspect the mortar rim and pestle head periodically for chips, which can shed small ceramic fragments into your sample.