Don't poison your family

If something is swallowed

If a child or pet may have swallowed, breathed in or spilled a glaze material, call the poison line for your region now, even if they seem fine. Do not wait for symptoms. If someone is unconscious, not breathing, struggling to breathe or having a seizure, call the emergency number first.

This guide is not medical advice: a poison center, a doctor or a vet decides what to do. This page helps you reach them quickly and, better still, avoid needing to.

Numbers for

Choose your country to see who to call there.

We suggest saving your region's numbers in your phone today, and on a card inside the studio door.

What to have ready when you call

The material's name exactly as written on the bag or bucket, and its label or safety data sheet (SDS: the supplier's sheet of a material's hazards and first aid). A photo of the bag works.
For a mixed glaze, its recipe. Your Glazecalc recipe is the glaze's ingredients list.
Roughly how much, and when.
How: swallowed, breathed in, on the skin or in the eyes.
Any symptoms so far.
The child's or pet's approximate weight, since the same amount matters more to a smaller body. For a pet, also its breed, age and any health problems.

What not to do

The NHS advises: do not try to make the person sick, and do not give them anything to eat or drink. With a pet, do nothing until the vet or animal poison line tells you what to do.

If you go to hospital, the NHS says to take the packaging or a sample if it is safe to do so. For a glaze material, that means the bag's label or the safety data sheet.

What is most dangerous to swallow

Glaze materials can harm a family in two different ways:

The acute danger (harm from one dose, within hours) is swallowing a soluble material, one that dissolves in water or stomach acid. Locked storage and the numbers above deal with it.
The chronic danger (harm from many small doses) is dust, mainly silica and lead, which causes no symptoms at first and travels home on clothes. Clean habits deal with it.

Most of a glaze is silica, kaolin and feldspar, which barely dissolve. We treat them as a long-term breathing hazard rather than a swallowing emergency. The soluble materials below are the ones to lock away first.

Soluble glaze materials: what they do if swallowed
Material	What it does	Reported doses
Barium carbonate	Once sold as rat poison. It barely dissolves in water but does dissolve in acid, so treat it as soluble once swallowed. Barium drives down the potassium in the blood, causing vomiting, diarrhea and muscle weakness that can progress to paralysis, breathing failure and an irregular heartbeat. Symptoms typically begin within 2 hours.	Sources disagree. A WHO review estimates the lethal dose of barium absorbed from the gut at 3 to 4 g in untreated cases, with toxic effects from 0.2 to 0.5 g, and lists a lowest reported lethal dose of barium chloride, a soluble barium salt, of 11.4 mg per kg of body weight. An emergency-medicine reference gives a lethal range of 1 to 30 g for barium salts, with harm possibly from about 200 mg. None gives a figure for children, so call for any amount.
Borax and boric acid	Nausea, vomiting, diarrhea and stomach pain come first; vomit and stool may be blue-green. Severe cases bring a bright red rash that later peels, seizures, kidney injury and shock.	Rough lowest lethal doses: 2 to 3 g for an infant, 5 to 6 g for a child. In one review of 784 swallowings, only 12% caused symptoms and none were fatal, but deaths do happen, and there is no antidote.
Lithium carbonate	A child weighing 15 kg (33 lb) who swallowed 300 mg had a short spell of involuntary muscle spasms and overactive reflexes (acute dystonia and hyperreflexia), which passed.	Little has been written about young children. 300 mg is far less than a spoonful of powder.
Soda ash (sodium carbonate)	Dissolves readily in water. We found no reliable figures for what it does to a child.	None found. Call for any amount.
Potassium dichromate	A chrome colorant used in some recipes. Fisher Scientific's safety data sheet warns that it "May be fatal if swallowed", causes burns in the gut and may damage the kidneys. The same sheet warns that it "May be fatal if inhaled" and may cause cancer, and of a "possible risk of harm to the unborn child".	Not established, and safety data sheets disagree on how toxic it is.

These harmful amounts run from a few hundred milligrams to a few grams. Glaze materials are sold by the pound or kilogram, so one open bag or bucket holds far more than enough to harm a toddler.

Colorants and lead

Colorants are the metal oxides and stains that give a glaze its color: copper, cobalt, chrome, manganese, nickel, cadmium-selenium stains and others. A university ceramics safety page names lead, cadmium, cobalt and chromium among the especially hazardous glaze ingredients. We found no reliable dose figures for any colorant, so call for any amount. A bucket of mixed glaze holds the same materials as the bags it came from, only wet.

Lead's main danger is different: not one spoonful, but small amounts of dust swallowed over weeks or months, with no warning signs (see Lead and children, below).

Storing materials at home

No official body sets rules for storing glaze materials at home, but health and safety pages agree: keep the work in its own space, away from children. Pennsylvania's health department, writing about hobbies that use lead, says to "Utilize a designated workspace or garage for your hobby and keep children away from this area."

A storage checklist

These are general poison-prevention rules applied to glaze. No ceramics standard sets them, but we suggest all of them:

Keep dry materials locked away: a cabinet, or a room, garage or shed that locks. A high shelf helps, but children climb. If you can lock up only a few things at first, start with the soluble materials and colorants.
Keep materials in their original bags or tubs. If you move one into another container, label it with the name exactly as written on the bag.
Never use food or drink containers (yogurt tubs, jars, bottles) for glaze materials, even labeled. A child knows what a yogurt tub holds.
Keep studio tools (scoops, spoons, whisks, sieves, scales) in the studio. Never use kitchen tools for glaze, or glaze tools for food.
Keep wet glazes in labeled buckets with the lids on.
Keep each material's safety data sheet with it, on paper or on your phone.
Keep nothing from the studio in the kitchen: no bags, buckets, tools or test tiles.

For buying and storing materials in more depth, see How to make a glaze.

Glaze waste and rinse water

Never pour glaze, or water you have rinsed glaze tools in, down the sink or onto the garden. The UK Crafts Council suggests a separate bucket of water for washing hands, brushes, sieves and tools. Let it settle overnight, pour off the clear water, then dry the settled glaze and put it in the trash (it goes to landfill), never down the drain.

We suggest a lid on that bucket: the sludge holds the same metals as the glaze, and pets drink standing water. Disposal rules vary from place to place, so check each product's safety data sheet, and ask your local council or water company if you are unsure.

Keeping dust in the studio

Pennsylvania's health department puts the problem plainly: "Lead-contaminated dust from your hobby can attach to your clothes, shoes, hair, skin, and personal items, and readily transfer into your vehicle and onto surfaces in your home." The CDC adds that adults "may bring lead home with them and expose their families to lead without knowing." The Pennsylvania guidance gives the remedy:

Wash your hands before eating.
Change out of your studio clothes and shoes before you go into the house.
Wash studio clothes separately from the family's laundry.
Vacuum the house and car regularly with a HEPA vacuum (one with a high-efficiency filter that traps fine dust).

House rules we suggest

No clay or glaze work on the kitchen or dining table, even for a quick job.
Clean the studio wet. A university ceramics safety page says to avoid dry sweeping, vacuum only with a HEPA filter and wet-mop daily. Wet-wipe surfaces after each session too.
Treat all glaze dust like lead dust, even if your glazes are lead-free. Dust carrying barium, chrome, cobalt or manganese travels home the same way.
Scrub your hands and nails before you pick up a child, make food or stroke a pet.
Keep children from playing in the studio, and don't let it become a shortcut to the yard or garden.

Pregnancy and breastfeeding

We suggest extra care if anyone at home is pregnant or breastfeeding. Keep them out of the studio while you handle dry materials, and if you have used lead, ask their doctor or midwife whether a blood lead test makes sense for the household.

For controlling dust while you work (respirators, wet methods and ventilation), see Safe mixing and ventilation.

Lead and children

Lead is the quiet risk. The CDC lists "Mixing or applying glaze or pigments containing lead" among the hobbies that can expose people to lead, and warns that "Most children and adults who are exposed to lead have no symptoms." In its words, "The only way to tell if you or your child has been exposed is with a blood lead test."

Why children take in more

Children take in more household dust than adults do. They breathe more air for their body weight, and the US EPA notes that young children "often have higher rates of soil and dust ingestion because of their unique behaviors such as crawling and hand/object-to-mouth contact." For lead, the dust a child swallows from floors, hands and toys matters more than what they breathe.

The blood test and the 3.5 number

Blood lead is measured in µg/dL (micrograms of lead per deciliter, a tenth of a liter, of blood). The CDC's blood lead reference value is 3.5 µg/dL, lowered from 5 µg/dL in 2021. It is the level that 97.5% of US children aged 1 to 5 fall below, so a child at or above it has more lead in their blood than almost all children their age. The CDC says the value "is not health-based and is not a regulatory standard", and when it lowered the value it said "Lead exposure at all levels is harmful to children."

So 3.5 µg/dL is a flag for follow-up, not a safe limit. A result below it does not mean lead did no harm. A result at or above it means finding where the lead is coming from; the CDC's guidance is to confirm a finger-prick result with a sample from a vein. Doctors outside the US use their own guidance, and yours will explain what a result means.

What we suggest

Use lead-free glazes where you can. In a home with young children, we suggest not using lead at all.
If you have used lead frits (lead already melted into a glass and ground to powder), or old glazes whose make-up you do not know, ask your child's doctor about a blood lead test.
Follow the dust rules above for every glaze, not only the ones with lead.

Glazecalc keeps lead off unless you choose it in Settings. With lead off, it never adds lead to a recipe or suggests it.

Pets

We found no veterinary study or guidance written for pets in potters' homes. The advice in this section is common sense, built on general facts about lead, barium and birds. It does not come from a veterinary source.

What is known

The Pet Poison Helpline says "Lead is toxic for all species, but young and/or malnourished animals are at highest risk for poisoning", with signs such as vomiting, diarrhea, not eating, stumbling, seizures and blindness. A veterinary case report describes a dog that ate sparklers containing barium nitrate (a soluble barium salt, not a glaze material): it developed sudden weakness, drooling and an irregular heartbeat, and recovered with veterinary treatment. Birds are a special case: a University of Illinois vet explains that "Birds have a highly sophisticated and ultra efficient respiratory system, making them particularly vulnerable to the inhalation of fumes and aerosols."

Common-sense rules

Keep pets out of the studio, with the door shut.
Dogs chew bags and drink from buckets. Keep bags in a closed cabinet and a lid on every bucket.
Cats walk through dust and lick it off their paws and fur. Wet-clean the floor and keep cats out of the studio, so there is nothing to groom off.
Birds and small mammals (rabbits, guinea pigs, hamsters) share the household air. Keep them in a far room with the door shut while you handle dry materials and while the kiln fires.
Fish tanks collect settling dust. Keep them out of the studio, and covered.
Keep pet food and water bowls away from the studio and kiln, and use commercial or tested bowls, not studio experiments.

If a pet may have eaten or drunk anything from the studio, or shows signs like those above, call your vet or an animal poison line (see the table at the top), with the material's name and the pet's weight to hand.

The kiln

The outside gets hot enough to burn

A UK schools risk assessment says a kiln's outside "can reach 160 °C and possibly more" (about 320 °F), and a school kiln guide reports metal bands at up to 460 °F (about 240 °C). Skutt, a kiln maker, recommends a kiln room that can be locked against children and pets. Where a room cannot be locked, the school guide suggests a barrier such as a kiln safety screen.

Small children and pets cannot understand a warning sign. We suggest keeping them behind a locked door or a barrier while the kiln fires and while it cools, and posting a warning sign for everyone else.

Space around it

Sources disagree on clearance. Rio Grande says at least 12 inches (30 cm) from walls and anything combustible. L&L strongly recommends 18 inches (46 cm) to all walls, and the building code it cites asks for 3 feet (0.9 m) from combustible walls. Follow your kiln's manual and local fire code; if you are unsure, allow 18 inches from any wall and 3 feet from anything that can burn. In a garage, keep cars, fuel and paint well away.

Power

Rio Grande recommends a dedicated circuit (one that powers nothing else) with a properly grounded outlet. We suggest no extension cord. Between firings, switch off the kiln's breaker or disconnect switch, or unplug it, so a child cannot start it.

Be there when the firing ends

A kiln sitter is the mechanical switch on many manual kilns: a small cone bends at the end of the firing and trips the switch off. Its manual says it "is NOT intended to perform as a fail-safe shut-off device." Rio Grande says never to leave a firing kiln unattended, "especially near the expected shut-off time". So stay nearby and check the kiln while it fires, above all near the end; fire only when an adult will be home and awake through the whole firing, check that it has switched off, and keep an ABC fire extinguisher in the kiln room. For how sitters, controllers and schedules work, see Firing a basic kiln.

Fumes and carbon monoxide

Firing gives off fumes, so vent the kiln to the outdoors; Safe mixing and ventilation explains how. A kiln in an attached garage needs venting that keeps fumes from reaching the house through the connecting door. Keep birds in a far room whenever the kiln fires.

Carbon monoxide (CO) is a poisonous gas you cannot see or smell. A university kiln safety sheet requires CO alarms with gas kilns. Views differ for electric kilns, but burning off organic matter (in clay, or things like paper or wax) can make CO. We think a CO alarm in the kiln room and the rooms next to it is a sensible, inexpensive step for any kiln.

Peepholes and eyes

Infrared light, which you cannot see, "starts at 752°F (400°C)", and the Ceramic Arts Network says looking into a kiln above this should always be done with eye protection. Infrared can damage the lens of the eye and lead to cataracts, and long gazing can injure the retina. Sunglasses and didymium glasses do not block it.

Children should not look into a kiln at all. A glowing peephole draws them, and they will not reliably keep protective glasses on, so keep them away while the kiln is hot. Adults should look only briefly, through IR-rated welding glasses. Sources recommend shades from 1.7 to 5; shade 3 is a sensible choice, darker if you see spots afterward.

Handmade ware on the family table

The question for pots on the family table is leaching: metals dissolving out of the fired glaze into food or drink. The FDA warns that if pottery "is not manufactured properly, this lead can leach into food and drink", and that "no amount of washing, boiling, or other process can remove lead from pottery." Regulators such as the US FDA and the EU limit how much lead and cadmium a finished piece releases in a standard acid test, not what the glaze contains. The strictest US limit, for cups, mugs and pitchers, is 0.5 µg/mL of lead.

Lead-free is not the same as food-safe

A glaze with no lead can still leach. Digitalfire, a glaze chemistry reference, names glazes containing "heavy metal oxide colorants, barium, lithium, or lead" as the concern, and warns that a stain fired above its rated temperature can release cadmium. The ASTM D-4236 art-materials label on a jar "DOES NOT establish that a fired glaze is food-safe", and "Tableware producers must test all finished ware to establish dinnerware status."

"Food safe" means this glaze, on this clay, fired to this cone, applied this way, releases less than the legal limits. A recipe calculation, Glazecalc's included, can flag a risky recipe but cannot prove a pot is safe. Only a leach test of the fired piece can.

We suggest reading a "food safe" label on a commercial glaze as a good start, not a guarantee: a different clay, a thicker coat, another cone or a second glaze on top changes the result.

Testing

Laboratories test fired pieces with a standard acid soak that represents a worst case, such as ASTM C738 in the US. One lab's EU test needs four identical pieces and takes seven working days, so make spares of anything you plan to have tested.

Home tests are disputed. The FDA says home swab kits can show leachable lead, and that a piece that tests positive should not be used for food. Ceramics NZ warns that consumer lead-test pens are "not designed for this use" on ceramics and can give false positives. Digitalfire suggests leaving a lemon slice on the glaze overnight as a rough screen. The safe reading: a positive home test means stop using the piece for food, and a negative one proves nothing. Only a lab can tell you a piece is safe.

Crazed ware

Crazing is a network of fine cracks in the glaze surface, and sources disagree about it. A Ceramics Monthly experiment found crazed tiles could be cleaned, best in a dishwasher, though they came out less clean than uncrazed tiles after soap and water. Digitalfire holds that "Crazed ware is unacceptable" and that crazing "severely weakens ware". The safe course is simple: do not use crazed pieces for food.

Liner glazes

A liner glaze is the glaze on the inside of a cup or bowl, where the food sits. Digitalfire describes a liner that may be low enough in risk to use without lab testing: no colorants, barium, lead or lithium; fully melted; no crazing; and it wears well. Even then, only a leach test of your own fired pots shows whether they are food-safe. Warning signs in any glaze are heavy amounts of colorant, crystals on the surface and poor melting.

Family rules we suggest

Children's cups, bowls and plates: only lab-tested, durable liner glazes, or commercial dinnerware.
Do not store acidic food or drink (citrus, tomato, vinegar, fruit juice, wine) in pots glazed with anything you have not had tested.
Do not use crazed pieces for food.
Test tiles and experiments stay in the studio, never in the kitchen, the toy box or the pet's bowl.
Take care with other pottery too. The FDA advises caution with handmade or crude-looking pieces, antiques, damaged or worn pieces, flea-market finds and bright orange, red or yellow decoration.
If a child has used pottery you now doubt, the FDA says to talk to a doctor about a blood lead test.

For more on how glazes melt, why some leach and what the limits mean, see Glazing from first principles.