Food safe glaze: the rules for selling mugs and dinnerware

What food safe glaze means when you sell pottery

The FDA does not approve glazes in the jar. Its two compliance policy guides, CPG Sec. 545.450 for lead and CPG Sec. 545.400 for cadmium, look at the finished article: how much lead and cadmium a glazed surface releases into a leaching solution, measured on 6 units. Above those levels, the FDA may recommend legal action or detain imports. The FDA also states that no FDA regulation authorizes lead as a food additive, including as a component of foodware.

So for a potter selling mugs, bowls and plates, a food safe glaze is one that, on your clay and at your firing, leaches less than those levels. If ware is over the levels, the FDA may be treated as adulterated under section 402(a)(2)(C) of the Act. According to Mayco, foodware may contain traces of lead or cadmium if it tests below the FDA thresholds. The question a buyer or a regulator asks is how much leaches, not whether the glaze lists lead as an ingredient.

This page covers the US federal levels, California's Proposition 65 warnings and how to word your listings. It does not say whether any glaze or piece is safe. Rules vary by state and city, and this page is general information, not legal advice.

FDA lead and cadmium limits for ceramic ware

The FDA sorts ceramic ware by shape. Flatware, such as a plate, has an internal depth that does not exceed 25 mm. Anything deeper is hollowware. Small hollowware has a capacity of less than 1.1 liter, and large hollowware has a capacity of 1.1 liter or more. Cups and mugs have their own lead level, and the lead guide notes they usually have about 240 mL or 8 fl. oz.. The levels are micrograms of metal per millilitre of leaching solution.

The cadmium guide has no separate rows for cups, mugs or pitchers, so those pieces take the small or large hollowware cadmium level according to their capacity.

Mugs and pitchers carry the strictest lead levels. The lead guide defines cups and mugs as vessels for drinks such as coffee or tea at above room temperature, and pitchers as vessels for fruit and vegetable juices or other acidic beverages. The cadmium guide notes that cadmium is extractable by acid foods. For imported ceramicware, the FDA lists Import Alert 52-08 for lead and cadmium.

Lead in pottery and lead in ceramic glaze: why a glaze can fail after your own firing

Lead in pottery has historically come from the glaze. The FDA notes that lead compounds, such as lead oxide, have historically been used in glaze formulations, and that, when fired at inadequate or uncontrolled temperatures, lead is not fully bound into the glaze and can leach into food. The FDA levels are measured on the finished article, so the fired surface is what counts, not the recipe on the jar.

Glaze makers rate their products under set conditions. Mayco, for example, rates a glaze suitable for dinnerware only when fired according to the manufacturer's instructions, and its page lists layering, mixing, clay body, application thickness, firing temperature and firing atmosphere as things that can change the final surface. Mayco also states that finishedware producers bear responsibility for food-contact testing of ware sold.

That leaves several ways a glaze sold as food safe can fail on your piece:

• Firing to a different temperature. Asked whether dinnerware suitability changes at a different firing temperature, Mayco answers: It can. It recommends using test cones that confirm your ware reached the proper temperature for vitrification.
• Layering a dinnerware glaze over or under a decorative one, or mixing two glazes.
• Applying the glaze thicker or thinner than the maker tested.
• A different clay body or firing atmosphere.
• A fired surface that is not chemically durable, absent of surface texture, which is how Mayco describes a glaze suitable for dinnerware.

An art-materials safety seal does not settle the question either. Mayco states that an ACMI AP or CL seal does not mean a glaze is suitable for dinnerware: the seal covers handling the wet glaze, not food contact on a fired piece.

How lab leach testing works for food safe glaze on mugs

The FDA guides name ASTM method C738 among the methods for measuring lead and cadmium. A lab runs it on finished ware, and the result is what you can point to when you describe a piece as made for food.

1. Fire test pieces the way you sell them

   Use the same clay, glaze combination, thickness and firing schedule as your production ware. A test of a different glaze or kiln load tells you little about the pieces you list.

2. Send finished ware to an accredited lab

   ASTM C738 measures lead and cadmium extracted by acetic acid from glazed ceramic surfaces. ASTM describes it as a severe test unlikely to be matched in normal use. Ask the lab how many pieces it needs, since the FDA levels are judged on 6 units.

3. Compare results with the right category

   Read the lead and cadmium results against the row for that shape: cups and mugs, flatware, small or large hollowware, or pitchers. A mug result is judged against 0.5 micrograms/mL, any one of 6 units for lead.

4. Keep the report with a date

   Store the lab report, the glaze names and the firing schedule together. When you change a glaze, a clay body or a kiln, test again, because the old result no longer describes the new ware.

California Proposition 65 and ceramic ware

California adds a warning law on top of the FDA levels. Under Proposition 65, a business must warn a person before "knowingly and intentionally" exposing that person to a listed chemical. The California Attorney General's FAQ gives the example of a product that lacks a warning that users will be exposed to more than 0.5 micrograms of lead per day, and states that meeting a federal standard does not replace a Proposition 65 exposure assessment.

Ceramic ware has a history under the law: the Attorney General lists ceramic tableware is among products reformulated after notices or litigation. Lawsuits can be brought by the Attorney General, by some district and city attorneys, and by private parties acting in the public interest. Cases can end in settlements that set warning or reformulation terms. The Attorney General notes that voluntary compliance with an existing settlement may or may not give protection, so following another company's settlement is not a guarantee.

Two points matter for small potters. Under the law, businesses with 9 or fewer employees are exempt from its requirements. Businesses that violate it face up to $2,500 per day for each violation.

Lead free glaze and other listing wording

A listing describes the piece to buyers, so treat its wording like a label. The FDA's guidance on traditional pottery says ceramicware that leaches lead should not be labeled "Lead Free". If ware labelled that way contains extractable lead, the FDA may consider the term false and misleading, and therefore the ceramicware misbranded. Glaze makers are moving away from these words too. Mayco states that products will no longer be labeled "Lead-Free". It also explains that terms with the word safe can be interpreted differently depending on an artist’s language, country, regulatory environment, and local compliance requirements.

Plain, checkable wording holds up better than a promise. The table shows example wording that describes what you did instead of claiming a result.

How to label decorative-only pieces

A piece that looks like a mug or bowl is treated by the FDA as food ware unless it carries the labels set out in 21 CFR 109.16. A note in the listing or on the packaging does not replace those labels. The FDA's guidance notes that users may treat pottery as food ware after the packaging is discarded and/or the stick-on label is removed.

Under the lead guide, a piece is considered unsuitable for food use if it has a hole bored through the food surface, meaning a hole bored through the potential food-contact surface, or both of these labels:

1. A conspicuous stick-on label, on a surface buyers can see, with letters at least 3.2 mm (0.125 inches), stating one of the set messages, such as "Not for Food Use. May Poison Food," or one of two other set messages.
2. The same message as a permanent statement molded or fired onto the exterior surface of the base, in letters of the same height.

The cadmium guide names its own message, "Not for Food Use - Article May Poison Food.", on a permanent label on the back or base of the piece.

Mayco describes its decorative glazes as not recommended for the food-contact or lip and rim areas of dinnerware. Keep such glazes off the inside and the rim of any piece sold for food.

Rules for food-contact articles can also differ by state and city. Check with your state health department if you sell pottery at markets or to restaurants.

How this page is kept current

Every level and rule here was read on the FDA's compliance policy guides, the FDA's pottery guidance, the California Attorney General's Proposition 65 FAQ, the ASTM C738 page and Mayco's dinnerware page, checked on 3 Oct 2026. The page is re-checked every six months, and sooner if one of those sources changes. Glaze makers also update their ratings, so read the current label and product page for each glaze you use.

Where Nation fits

Questions about food safe glaze