TL;DR
Clean a pizza stone by scraping it dry -- no soap, no soaking, and as little water as possible. Unglazed stone is porous and absorbs whatever liquid touches it, so detergent flavors your next pizza and absorbed water can crack the stone when it heats. Dark staining is normal and is not a sign the stone is dirty.
Why a stone is not like a pan
A pizza stone is unglazed cordierite or clay. It works because it is porous: it pulls moisture out of dough, which is what produces a crisp base.
That same porosity means the stone is a sponge. Soap goes in and does not come back out with a rinse, so it evaporates into your food the next time the stone heats up.
Absorbed water is worse. A saturated stone put into a hot oven turns that water to steam inside the material, and the pressure can crack the stone. It is one of the most common ways a stone is destroyed.
So the entire method is built around keeping liquid out. Porous materials all follow this rule, which is why a mortar and pestle is also cleaned without soap, and it is a recurring theme in the guide to cleaning kitchen tools without damaging them.
How do you clean a pizza stone?
Let it cool completely, then scrape off stuck food with a bench scraper, a stiff plastic scraper, or a dry stiff brush. Wipe the surface with a barely damp cloth if needed and let it dry fully. Never use soap, never soak it, and never put it in the dishwasher.
The routine, step by step
1. Let it cool completely, in the oven. A hot stone meeting cool air or a cool countertop can crack from thermal shock. Leaving it in the oven as the oven cools is the safest approach.
2. Scrape the surface. A metal bench scraper, a stiff plastic scraper, or a dough scraper takes off burnt cheese and stuck crust. Work flat across the surface.
3. Brush the crumbs off. A dry stiff brush or a dry cloth. Do this over a sink or outside because it makes a mess.
4. Wipe with a barely damp cloth if needed. Barely damp, and only if scraping left a smear. Do not run the stone under a tap.
5. Let it dry completely before use. If any moisture got in, give it a full day, or heat the empty stone slowly in the oven to drive the moisture out gradually.
Dealing with really stuck residue
Burnt cheese welded to a stone is the usual complaint.
The dry approach comes first: cool, scrape hard with a bench scraper, then brush. Most of it will come.
If something remains, a paste of baking soda with a very small amount of water can be applied to that spot only, scrubbed with a brush, and wiped off with a barely damp cloth. Use as little liquid as possible and let the stone dry thoroughly afterward.
There is also a heat method. Run the stone in the oven at a high temperature for an hour so the residue carbonizes, let it cool completely, then scrape the ash off. Check the manufacturer's maximum temperature first, and be aware this can produce smoke, so ventilate the kitchen.
Do not use oven cleaner, degreasers, or bleach on a stone. All of them are absorbed and none of them can be rinsed out, and bleach must never be combined with ammonia, with vinegar or any other acid, or with rubbing alcohol, because each of those combinations releases a toxic gas.
Stains are not dirt
A used pizza stone turns brown and then nearly black, unevenly, and this is normal.
The dark color is absorbed and polymerized fat, the same substance that forms seasoning on cast iron. It does not make the stone dirty, it does not affect flavor, and many bakers consider a dark stone better because it holds heat well.
There is no way to return a stone to its original pale color, and trying to force it with chemicals or heavy soaking causes real damage.
Judge a stone by whether it cracks, smells burnt in use, or smokes heavily, not by its color.
Cracks, and how stones break
Stones crack for three reasons, and all of them are avoidable.
Thermal shock. Putting a cold stone into a hot oven, putting frozen food on a hot stone, or running water over a hot stone. Always heat a stone with the oven from cold, and let it cool in the oven.
Absorbed moisture. A stone that has been soaked, washed, or stored somewhere damp turns that water to steam inside the material when heated.
Physical impact. Dropping it, or knocking it against a rack.
A hairline crack is usually not fatal. A stone often keeps working with one, though it may eventually break into pieces along that line, at which point it needs replacing.
Storage and use habits
Store it in the oven. Many people leave the stone on a lower rack permanently. It evens out oven temperature and it is never subject to a sudden temperature change.
Use parchment or semolina rather than oil. Oil is absorbed and goes rancid inside the stone. Semolina or cornmeal on a peel does the release job.
Do not oil or season a pizza stone. It is not cast iron. Seasoning develops on its own from use, and adding oil deliberately just creates smoke and rancid odor.
Give it a full preheat. Forty five minutes to an hour at temperature is standard for a proper crust, and it also drives off any absorbed humidity gradually.
Keep it dry between uses. In a damp Oregon winter, a stone stored in a cold garage or a basement will take on moisture from the air.
Cast iron follows related but different rules, since it is metal rather than stone -- see how to clean a cast iron grill press. Metal bakeware tolerates the water and soap a stone cannot, as described in how to remove carbon buildup from baking sheets.
Cleaning a stone reduces smoke and residue. It is not a food safety program on its own.
Source: USDA Food Safety and Inspection Service guidance on cleaning food contact surfaces
FAQ
Can you wash a pizza stone with soap?
No. Unglazed stone is porous and absorbs detergent, which does not rinse back out and evaporates into your food the next time the stone heats. Scrape the stone dry with a bench scraper and brush off the crumbs instead, using a barely damp cloth only if needed.
Why is my pizza stone black?
Because absorbed fat has polymerized into a dark layer, exactly as seasoning does on cast iron. It is normal, it does not affect flavor, and it cannot be reversed. Judge a stone by whether it cracks or smokes heavily in use, not by its color.
How do you get burnt cheese off a pizza stone?
Let the stone cool completely, then scrape hard with a metal bench scraper and brush off the debris. For a stubborn spot, apply a baking soda paste with very little water to that area only, scrub, wipe with a barely damp cloth, and let the stone dry fully.
Can a pizza stone go in the dishwasher?
No. A dishwasher soaks the stone with water and detergent, both of which are absorbed. The detergent taints future food and the trapped moisture can turn to steam and crack the stone the next time it is heated in the oven.
Why did my pizza stone crack?
Almost always thermal shock or absorbed moisture. Putting a cold stone into a hot oven, placing frozen food on a hot stone, running water over a hot stone, or heating a stone that was recently soaked all cause it. Heat and cool the stone with the oven.
Should you oil or season a pizza stone?
No. A pizza stone is not cast iron, and added oil is absorbed into the pores where it goes rancid and produces smoke. Seasoning develops naturally from use. For release, use parchment or a dusting of semolina or cornmeal on a peel.
Stones are low maintenance once you know the rules. The oven and the kitchen around them take real time. If you would rather hand that off, get a quote or read more about house cleaning services.