Cadmium in Ceramic Glazes: A Buyer's Checklist

Cadmium in ceramic glazes is mostly a color problem. The bright reds, oranges and yellows that give pots and mugs their punch usually come from cadmium pigments, and a properly fired glaze locks them inside the glass. The pieces worth a second look are painted interiors, decorated rims, souvenir pottery and any color that sits on top of the surface.

The route into your food runs through the surface that touches it. The ATSDR's toxicological profile for cadmium lists ceramic glazes and pigments among the sources of exposure and notes that cadmium builds up in the kidneys, where its biological half-life runs to 10 to 30 years. What gets in leaves slowly, so the mug you drink from every morning deserves more scrutiny than the platter you use twice a year. Where the color sits on a piece decides the rest, and a hand-painted lip is as close as decoration can get to your mouth.

The short version

Seven checks cover almost every piece you will pick up, and none of them need equipment.

• Check the inside first, color that touches food matters more than outside decoration.
• Run a fingernail over the pattern, raised or slightly rough means an overglaze.
• Acid and heat pull more from a glaze, so skip decorated bowls for leftovers.
• Soak a suspect mug half full of white vinegar for 24 hours, then compare.
• Read the base for a maker and a country, a blank base under heavy decoration tells you nothing.
• Ask for a leachable lead and cadmium test report, the FDA level for a cup is 0.5 ppm of lead.
• Retire anything crazed, chipped through the glaze, or stamped for decorative use only.

Why bright red and orange glazes are the ones to check

Vivid warm colors are hard to produce in a kiln without cadmium, and the alternatives are thin. Cobalt gives blue, chrome gives green, iron gives the browns, and all of them ride through a high firing without complaint. Cadmium sulfide yellows and cadmium sulfoselenide scarlets are fussier about temperature. A stoneware glaze gets fired to somewhere around 2,200°F, and at that point a well-made glaze is glass with the colorant dissolved into it and locked in place. To keep the warm shades vivid, plenty of production applies them afterwards as an enamel or a decal, fired much cooler at roughly 1,400°F, so the color ends up as a thin layer resting on the finished glass. That layer is softer than what sits under it. Knives score it and a dishwasher cycle dulls it. Two mugs can look identically red on a shelf and behave completely differently in a kitchen, and the shelf gives you no way to tell them apart.

Which pots and mugs carry the most risk

Handmade and imported pieces sit at the top of the list, along with anything vintage that came out of a relative's cabinet. Market pottery bought on holiday, terracotta bean pots, brightly painted serving bowls and old dinnerware webbed with fine cracks all belong in the check-it-first pile. So does anything stamped "for decorative use only" or "not for food use" on the base. That wording is a statement from the maker about what the piece was tested for, and it means what it says.

A ceramic-coated frying pan belongs to a different category. Its surface is a silica-based coating sprayed and cured onto aluminum, and no pigment is fired into a clay body anywhere in the process. Wear and release drive that decision, and we compared the two surfaces in ceramic versus nonstick cookware. Mass-market stoneware from a large retailer is usually in-glaze color with compliance testing behind it. An unmarked handmade bowl comes with neither.

How to inspect a piece before you buy it

A 5 minute check with the piece in your hands gets you most of the answer, and the same pass works on what you already own.

1. Turn it over. Look for a maker, a country of origin and wording like "food safe" or "lead and cadmium free". A blank base under a heavily decorated piece tells you nothing.
2. Find where the color lives. Interior color and rim color touch food every time the piece gets used. Color on the outside wall has a longer way to travel.
3. Drag a fingernail across the pattern. Smooth and continuous with the gloss around it points to in-glaze color. A raised edge, a slight grit or a visible outline points to something applied on top.
4. Tilt it toward a light and look for crazing, the fine crack network that opens up the clay body under the glaze.
5. Study the top 20 mm of a mug. That band is where your lips ride, and painted rims and metallic gold lines are the worst possible place for decoration.
6. Ask the seller for a leachable lead and cadmium test report. Serious manufacturers run that test and can produce the paperwork.

Are home lead and cadmium test kits reliable?

Consumer swabs give you a rough screen and nothing close to a laboratory measurement. The FDA's page on lead in food and foodwares explains that glazes and decorations on ceramicware can leach lead, sets guidance levels for how much may come out, and points out that consumer test kits may not detect lead below those limits. The numbers behind that compliance test are small. A cup or mug is held to 0.5 ppm of leachable lead, which works out to 0.5 mg per litre of test liquid, and the piece gets soaked in 4% acetic acid for 24 hours at room temperature to produce the sample. A clean swab is weak evidence, and a color change is worth acting on.

One home check tells you about the glaze itself, and it takes a day. Household white vinegar is roughly 5% acetic acid, close enough to the laboratory solution to be useful as a look test even though it measures nothing. Fill the suspect mug halfway, about 200 ml of plain white vinegar, cover it, and leave it on the counter for 24 hours. The dry band above the vinegar line is your control, from the same piece and the same firing. Pour the vinegar out, rinse, dry and compare the two bands under strong light, then wipe the soaked band with a white paper towel. Lost gloss, a chalky patch or pigment on the towel means the decorated surface is not holding up, and the piece should stop touching food.

What acid and heat do to a decorated surface

Vinegar, citrus and tomato pull at a glaze harder than anything else in a normal kitchen. Lemon juice sits at roughly pH 2, a simmering tomato sauce at roughly pH 4, and both spend real time against the wall of whatever holds them. The FDA's questions and answers on lead-glazed traditional pottery states that acidic food and heat increase how much lead comes out of such a glaze, and advises against using those pieces for cooking or for storing food at all. Storage is easy to forget. A decorated bowl of leftovers in the fridge is hours of contact with no cooking involved.

Washing does its own damage. Dishwasher water runs at around 150°F with alkaline detergent behind it, and that combination takes the shine off low-fired enamel and gold banding over time. Hand-wash anything painted. When we leave a lemon-dressed salad overnight in a decorated stoneware bowl, the painted band on the inside wall comes out visibly duller where the dressing sat.

Cadmium in ceramic glazes versus bare metal cookware

Stainless steel, cast iron and pure titanium carry no pigment of any kind, and that removes the question entirely. The color you see is the metal, so nothing has been painted or fired onto the food surface to wear through later. Our own pure titanium pots, pans and woks have no glaze and no coating at all. The tradeoffs move somewhere else, into heat response and how you preheat, and we put ceramic and titanium side by side on safety and everyday cooking.

Surface	Where the color comes from	What to watch for	Sensible use
High-fired in-glaze stoneware	Colorant dissolved into the glass	Crazing and deep chips	Everyday food and drink
Overglaze enamel or decal	Pigment fired on top at a lower temperature	Fading, dulling, knife marks	Outside decoration only
Traditional or souvenir pottery	Unknown glaze recipe, often low fired	Any contact with acid or heat	Display
Ceramic-coated pan	Silica-based coating over aluminum	Wear and sticking after months	Low to medium heat
Bare pure titanium	The metal itself	Nothing applied to the surface	Every cooktop, oven included

Lining the materials up next to each other is the fastest way to see what you are trading away, and we ran a longer version of that across nonstick, ceramic, stainless, cast iron and titanium.

FAQ

Is cadmium in ceramic glaze dangerous?

The answer turns on whether the pigment stays put. Cadmium bound into a high-fired glaze behaves like the glass around it and stays there under normal use. Decoration applied on top of a finished glaze is a softer layer that knives and acidic food can reach, and that is the situation health guidance is aimed at.

Is handmade pottery from a market abroad safe to drink from?

Treat it as display until you have paperwork. The FDA's guidance on traditional lead-glazed pottery advises against using those pieces for cooking, serving or storing food. The glaze recipe and the firing temperature are both unknown to the buyer, so a hand-painted mug from a holiday stall belongs on a shelf.

Are ceramic-coated pans a cadmium risk too?

Ceramic-coated cookware uses a silica-based sol-gel layer rather than a pigmented ceramic glaze, so the bright-color question does not apply in the same way. What those pans do have is a wear problem: the surface loses release over months of use and food starts grabbing. How to fix a sticky pan covers what to do when that starts.

Can you tell whether a glaze contains cadmium by looking at it?

Color alone will not tell you. Manufacturers also make reds and oranges from encapsulated stains that behave differently in the kiln and in use. What a piece does tell you is where the color sits, whether it feels raised under a fingernail, whether the glaze shows crazing, and whether the seller can produce a leachable-metals test report.

Sorting the cabinet you already own

Do it in one pass. Plain high-fired pieces stay in rotation. Decorated interiors, painted rims and gold banding move to display duty or to dry food that leaves in minutes. Anything crazed, chipped through the glaze or stamped for decorative use only stops touching food at all, and old souvenir pottery is the first thing to retire. Keep the vinegar test for the two or three pieces you actually care about, since 24 hours each adds up. For the cooking itself, the surface question disappears when there is no glaze and no decoration involved, which is the case for the uncoated titanium pans and pots in our best sellers.