What Is a Mortar and Pestle? A Plain-Language Guide

Last verified: October 6, 2026. A mortar and pestle is one of the oldest tools still in daily use. The mortar is a sturdy bowl, and the pestle is a heavy, blunt, club-shaped tool held in the hand. Material placed in the bowl is crushed, ground, or mixed by pressing and turning the pestle against it. In a laboratory it is used to reduce solids to a fine, even powder, to blend powders together, to break up lumps, and to grind tough biological material, often while it is kept cold.

The problem it solves is simple. Many procedures need a solid to be in small, uniform pieces so that it dissolves faster, reacts more completely, mixes evenly, or can be extracted. The mortar and pestle does this with no electricity, no moving parts to maintain, and almost no setup, and it gives the person using it direct feel for how the material is behaving as it breaks down.

How It Works

Two actions do the work. Crushing uses downward force to fracture hard or brittle pieces, and grinding uses a combination of pressure and a circular or rubbing motion to reduce them to progressively finer particles. The inner surface of the bowl and the head of the pestle are shaped so that material is caught between them and worked down. Sample sizes are usually small, from fractions of a gram to some tens of grams, depending on the size of the set.

Good technique matters because it affects the result: working in small amounts, scraping material from the sides back into the center, and grinding in stages tend to produce a finer and more consistent powder than trying to do everything at once.

Common Materials

The material determines what a mortar and pestle can do and what it can safely be used for. These are the ones most often seen.

• Porcelain — the standard, general-purpose laboratory choice. It is hard and chemically resistant, usually unglazed on the grinding surface so that it grips the material. It is relatively inexpensive but can chip and can leave tiny particles in very sensitive work.
• Agate — a very hard, dense natural stone with a smooth surface. It is used for fine grinding and when a sample must not pick up contamination from the tool, such as in some analytical sample preparation. It is more costly and can be brittle.
• Glass — smooth and non-porous, so it is easy to clean and does not absorb the sample. It suits mixing and gentle grinding of softer materials but is less effective on hard solids.
• Ceramic and alumina — very hard, wear-resistant options used for abrasive materials.
• Stainless steel and other metals — durable and unlikely to break, but potentially reactive with some samples and not suitable where metal contamination matters.
• Stone and wood — common in kitchens. They are porous and difficult to clean to laboratory standards, so they are not typically used for analytical or biological work.

Whichever material is used, it should be matched to the sample, because softer tool materials can wear into the sample and harder ones can damage a delicate material.

Who Uses a Mortar and Pestle, and Why

It appears across many fields, from chemistry and materials science to biology, pharmacy, geology, and food and plant science.

• Chemistry and materials — grinding crystals and powders before analysis or reaction, and blending solid reagents evenly.
• Geology and soil science — reducing rock, mineral, or soil samples to a fine powder for analysis.
• Plant and molecular biology — breaking open tough plant tissue to extract nucleic acids, proteins, or metabolites. A common approach is to chill the mortar and grind the tissue while it is frozen, so that it breaks easily and its contents are protected from degradation.
• Pharmacy and compounding education — combining powders and preparing small quantities, as part of training and in some small-scale preparation settings.
• Teaching laboratories — demonstrating particle size, mixing, and extraction with minimal equipment.

How It Differs From Mechanical Alternatives

A mortar and pestle is a manual tool, and it is worth understanding where it sits among related equipment.

• Homogenizer — a powered device that breaks up tissue or particles with high shear, usually faster and more reproducible across many samples. See what a homogenizer is.
• Sonicator — uses ultrasound to disrupt cells or disperse particles in a liquid, which does a different job from grinding a dry solid. See what a sonicator is.
• Bead mill or ball mill — shakes or tumbles a sample with hard beads inside a closed container to pulverize it. It handles many samples at once and gives more consistent results, with less operator variation.
• Blender or grinder — chops larger quantities quickly, though with less control over fineness.

The mortar and pestle remains the choice when a lab needs a few small samples, has no other equipment, wants to avoid cross-contamination between runs by using separate tools, or simply needs the quickest way to crush something. Its main limits are time, operator variability, and the physical effort of grinding larger numbers of samples.

Why It Matters for Research Administration and Lab Management

Because a mortar and pestle is inexpensive and simple, it is rarely a line item anyone reviews. A few practical points are still worth knowing.

• Cleaning and cross-contamination. Porous or scratched surfaces can hold residue from previous samples. Shared sets need a clear cleaning routine, and many labs designate sets for specific materials or purposes.
• Method consistency. Hand grinding varies from person to person. Where results must be comparable across people or over time, labs often write down the procedure or move to a mechanical method, which reduces variation.
• Dust and containment. Grinding powders can release fine dust, which is a hazard for some materials. Labs commonly consider ventilation or containment, such as working in a fume hood or enclosure, depending on the substance.
• Cryogenic work. Grinding frozen tissue involves very cold materials that call for training and appropriate protective equipment. Using materials that tolerate such temperatures is part of selecting a set.
• Breakage and replacement. Ceramic and stone sets chip and crack, and a damaged set can shed fragments into a sample. Inspection and replacement belong in routine lab upkeep.

Choosing and Caring for a Set

Because the tool is so simple, small choices make a large difference in how well it performs.

• Size. The bowl should be large enough that material does not spill when ground, but not so large that a small sample spreads thinly and is hard to gather. As a general rule, the sample should fill only a fraction of the bowl.
• Surface texture. A rougher, unglazed grinding surface grips material and grinds more effectively, while a smooth glazed or polished surface is easier to clean and better for mixing.
• Pestle fit. The head of the pestle should match the curve of the bowl so that material is caught between the two surfaces instead of sliding around.
• Sets, not single pieces. Bowls and pestles are usually sold together and matched to each other, so replacing only one half can leave a poor fit.
• Cleaning and storage. Rinsing promptly after use keeps residue from drying into the surface, and storing sets so they do not knock together reduces chipping.

A careful choice at purchase, and basic care afterward, keeps a set serviceable for many years and keeps results consistent between users.

A Note on Scope

This page is general information to help readers understand what the tool is and where it fits. It is not clinical or safety training. Always follow your institution’s procedures and any manufacturer instructions, particularly when grinding hazardous materials or working with very cold substances.

Frequently Asked Questions

What is a mortar and pestle used for in a lab?

It is used to crush, grind, and mix solids by hand: reducing crystals or powders to fine particles, blending reagents, and breaking up tough biological material such as plant tissue for extraction.

Which material is best for a laboratory mortar and pestle?

It depends on the sample. Porcelain is the usual general-purpose choice, agate suits fine grinding and work where contamination must be minimized, and glass is easy to clean and suited to softer materials. A tool material should never react with the sample.

What is the difference between a mortar and a pestle?

The mortar is the bowl that holds the material, and the pestle is the hand-held, club-shaped tool that presses and grinds against it.

Why is a mortar sometimes chilled before grinding?

For biological samples, chilling the mortar and grinding the tissue while frozen makes it brittle and easier to break up, and helps protect delicate components from degrading. Cold handling should only be done with proper training and protective equipment.

When should a lab use a homogenizer instead?

When there are many samples, when results need to be more reproducible between operators, or when the material is too tough or too plentiful to grind by hand in a reasonable time.

How should a mortar and pestle be cleaned?

Cleaning depends on the material and the sample, and it matters most for porous surfaces and for sensitive analysis. Labs generally follow a written cleaning procedure and check the manufacturer’s guidance for the specific material.