TL;DR
Pumice works because it is full of tiny sharp-edged pores, and those same pores fill with skin, soap, and moisture within a few uses. Scrub the stone with a stiff brush under running water every time you use it, then dry it completely somewhere outside the shower. Replace it once it feels smooth, crumbles, or smells, and never share one.
What pumice actually is
Pumice is volcanic rock. It forms when gas-rich lava cools so fast that the escaping bubbles freeze in place, leaving a stone riddled with microscopic voids.
Those voids are the point. The sharp edges around each pore are what abrade dead skin, and the porous structure keeps the stone light enough to float.
They are also the problem. Every pore that grinds off skin fills with skin, and each one holds a droplet of water afterward. Soap residue plugs them further, so a clogged stone stops working and starts holding moisture in a warm bathroom.
Synthetic pumice sponges behave the same way. So do the foot files with a mineral grit surface, covered in how to clean a foot file safely.
How do you clean a pumice stone?
Hold it under warm running water and scrub the working surface with a stiff brush or an old toothbrush until the pores are clear and the water runs clean. Add a drop of dish soap for a stone that has gone slick, rinse thoroughly, then set it somewhere with airflow to dry completely.
The routine, every single use
1. Rinse it immediately after use. Do not set it down and come back. Skin residue dries hard in the pores and becomes much harder to clear.
2. Scrub under running water with a stiff brush. An old toothbrush works. Work in small circles across the whole surface until the water passing through runs clear.
3. Use a drop of dish soap if it feels slick. Slickness means soap and oil residue. Rinse very thoroughly afterward, because soap left in the pores attracts more residue.
4. Shake off the water. Pumice holds a lot of it.
5. Dry it somewhere with airflow. Not the shower floor, not a soap dish, not a closed drawer. A ledge outside the shower, a rack, or a towel are all better. A stone that never dries is a stone that grows things.
6. Store it dry. Once it has fully dried, keep it somewhere ventilated.
The drying step is the same one that governs every damp bathroom item, which our guide to cleaning the personal items you use every day keeps returning to.
Deeper cleaning once a week
Scrubbing handles the daily load. Once a week, do something more.
Boiling. Natural pumice is volcanic rock and tolerates heat well. Drop the stone in boiling water for about five minutes, then remove it with tongs and let it cool and dry completely. This is the simplest way to sanitize a natural stone. Do not boil synthetic pumice sponges or anything with a plastic handle, which will melt or warp.
A diluted bleach soak. About one teaspoon of household bleach per quart of water, five minutes, then a very thorough rinse and full drying. Ventilate the room, and rinse until there is no smell at all, since this stone goes on skin.
A vinegar soak. One part white vinegar to three parts warm water for fifteen minutes, scrubbed and rinsed. Gentler, and it helps with mineral buildup from hard water.
Use one method per session. Never combine bleach with vinegar or with any other cleaner -- bleach plus an acid releases chlorine gas, and there is no version of that trade worth making.
Baking soda paste. For a stone clogged with soap film, a paste scrubbed in with a brush and rinsed off works well and involves nothing hazardous.
Do not put a pumice stone in a dishwasher. It sheds grit that clogs the filter, and detergent residue in the pores is difficult to rinse out.
Why does my pumice stone stop working?
A stone that has gone smooth or slippery is clogged with compacted skin and soap, or it has simply worn down. Scrub it hard under running water with a stiff brush and a drop of dish soap. If the surface is still smooth after that, the abrasive structure is worn away and the stone needs replacing.
When to replace it
Pumice is consumable. It wears down as it works.
Replace it when the surface feels smooth rather than gritty after a thorough scrub, when the stone has worn thin or is crumbling apart, when it holds a smell after cleaning, or when it has gone discolored in a way that will not scrub out.
For a stone used a few times a week, a few months is typical. Heavy use wears one faster.
Never share a pumice stone. It carries skin cells and, potentially, fungus or wart virus between people. Household members each get their own, the same rule that applies to razors and nail tools.
The safety part that matters more than the cleaning
Pumice removes callus, and callus exists for a reason.
Do not use a pumice stone on cracked, bleeding, irritated, or infected skin. Do not use one on a wart or a corn without medical advice, since abrading either can spread the problem.
Anyone with diabetes, peripheral neuropathy, or poor circulation should not use a pumice stone, a foot file, or any abrasive foot tool without talking to a doctor or podiatrist first. Reduced sensation means an injury can go unnoticed, and a small break in the skin on a foot with poor circulation can become serious.
Even for healthy feet, gentle is better. Use the stone on damp, softened skin after a shower, work lightly, and stop while there is still callus left. Removing too much makes skin more likely to crack.
Source: American Podiatric Medical Association consumer guidance on foot care
Keeping the bathroom from working against you
A stone dries faster in a room that dries faster.
Run the exhaust fan during and after every shower. Keep items off the shower floor and out of standing water. Use racks and caddies that drain.
The same conditions that keep a pumice stone from mildewing are what keep a brush and a bath pouf usable, described in how to clean a long handled back brush and how to clean a loofah, bath pouf, or sea sponge.
FAQ
Can you boil a pumice stone to sanitize it?
Natural pumice is volcanic rock and tolerates boiling well. Five minutes in boiling water, then remove it with tongs and let it cool and dry completely. Do not boil synthetic pumice sponges or any stone attached to a plastic handle, since those will melt or deform.
How do you unclog a pumice stone?
Hold it under warm running water and scrub the surface with a stiff brush or an old toothbrush until the water runs clear. Add a drop of dish soap or a baking soda paste for compacted soap film, then rinse thoroughly. If it stays smooth after that, the abrasive surface is worn out.
How often should you replace a pumice stone?
Every few months with regular use, and sooner if the surface has gone smooth, the stone is crumbling, or it holds a smell after cleaning. Pumice wears down as it works, so a stone that no longer feels gritty has reached the end of its useful life regardless of age.
Can two people share a pumice stone?
No. A pumice stone carries skin cells and can transfer fungal infections and wart virus between people. Everyone in a household should have their own, stored separately and dried fully between uses. The same rule applies to nail files, foot files, and razors.
Why does my pumice stone smell?
A smell means bacteria or mildew growing in pores that stay damp, usually because the stone lives on a shower floor or in a soap dish. Scrub it, sanitize it by boiling or with a diluted soak, and dry it fully outside the shower. If the smell survives that, replace it.
Is a pumice stone safe for diabetic feet?
Not without medical advice. Diabetes can reduce sensation and circulation in the feet, so a small abrasion may go unnoticed and heal poorly. Anyone with diabetes, neuropathy, or circulation problems should ask a doctor or podiatrist before using any abrasive foot tool at home.
Bathroom tools stay usable in a bathroom that actually dries out. If you would rather hand that job off, get a quote or read more about house cleaning services.