If you make or sell ceramic dinnerware, mugs, or pitchers, “FDA food-safe” isn’t about what’s in your glaze recipe — it’s about how much lead or cadmium actually migrates out of the fired piece when it touches food or drink. That distinction trips up a lot of makers and importers who assume a “lead-free” label settles the question.
Here’s exactly what the FDA measures, the numeric leachable limits by ware category, and how the test that determines compliance actually works.
Quick Answer
The FDA doesn’t set a maximum percentage of lead or cadmium allowed inside a glaze formula. Instead, it sets maximum leachable limits — how much of each metal is extracted from the finished, fired piece in a standardized acid test. For lead, the limits range from 3.0 micrograms per milliliter (µg/mL) for flatware down to 0.5 µg/mL for cups, mugs, and pitchers. For cadmium, limits run from 0.5 µg/mL (flatware and small hollowware) down to 0.25 µg/mL (large hollowware).
The Exact Leachable Limits by Ware Type
These thresholds come from two FDA Compliance Policy Guides: CPG 7117.07 / Sec. 545.450 (lead) and CPG 7117.06 / Sec. 545.400 (cadmium), both covering domestic and imported pottery and ceramicware used with food.
Lead limits: flatware (plates, saucers — internal depth of 25 mm or less) must average 3.0 µg/mL or lower across a 6-unit sample. Small hollowware other than cups and mugs (bowls, small dishes under about 1.1 liters) is capped at 2.0 µg/mL for any single unit in that sample. Large hollowware other than pitchers (serving bowls, casseroles 1.1 liters or more) is capped at 1.0 µg/mL per unit. Cups, mugs, and pitchers get the strictest limit of all: 0.5 µg/mL per unit, because they’re routinely used to hold hot coffee, tea, or acidic juice for extended periods — conditions that pull more lead out of a glaze.
Cadmium limits are simpler: 0.5 µg/mL for both flatware (as a 6-unit average) and small hollowware (any single unit in the sample), and 0.25 µg/mL for large hollowware. The cadmium guide doesn’t carve out a separate, stricter category for cups, mugs, or pitchers the way the lead guide does.
How the Compliance Test Actually Works
Testing labs fill the piece with a 4% acetic acid solution (standing in for acidic food or drink), let it sit for 24 hours at room temperature, then measure how much lead and cadmium ended up in the liquid. This extraction method is defined under ASTM C738 and corresponding AOAC methods, and it’s the basis both FDA’s own enforcement examinations and most third-party labs use when issuing a compliance certificate. FDA’s own guides describe examining a sample of 6 units per lot this way — that’s the agency’s enforcement sampling size for a given import lot or production run submitted for testing, not a rule requiring every maker to test every batch they produce.
This is why two glazes with the same lead content in the raw recipe can test completely differently once fired — firing temperature, glaze chemistry (silica and alumina content tend to lock metals into the glass matrix), cooling cycle, and even how evenly a piece was glazed all affect how much metal is available to leach. A glaze can be marketed as “low-lead” and still fail the leach test on an underfired piece, and a glaze containing lead at all can pass if it’s formulated and fired correctly.
Tips / Common Mistakes
Don’t assume a supplier’s “lead-free” or “food-safe” claim on a glaze bucket means your finished piece is automatically compliant — the only way to know is to test the fired ware, not the raw glaze.
Test actual production pieces, not just test tiles, since wall thickness, glaze application, and kiln placement all affect leaching results.
If you sell mugs, cups, or pitchers, treat them as the highest-risk category — they carry the strictest 0.5 µg/mL limit and are used with hot or acidic liquids, the exact conditions that increase leaching.
Retest after any change to your glaze recipe, clay body, or firing schedule — a passing result from last year’s batch doesn’t carry forward if any input changed.
If you sell in California, check state requirements separately. California’s Health and Safety Code has its own ceramicware leaching provisions that track closely with the federal limits but are enforced independently, so a federal pass doesn’t automatically cover state-level obligations.
Interior/food-contact surfaces are what’s tested and regulated — decorative glaze on the exterior or underside of a piece that never touches food isn’t subject to the same scrutiny, though many makers hold the whole piece to the same standard for simplicity.
Explore more: More packaging and food-contact compliance guides.
FDA lead and cadmium limits for ceramic glaze FAQs
Does the FDA ban lead in ceramic glaze entirely?
No. The FDA doesn’t prohibit lead or cadmium in glaze formulas outright — it limits how much of each metal can leach out of the finished, food-contact piece when tested, using the limits above. A glaze containing lead can still be compliant if it’s formulated and fired so that little to none of it migrates into food or drink.
Do I need to test every single piece I make?
No. FDA’s own compliance guides describe examining a 6-unit sample per lot as the agency’s enforcement testing protocol — that’s how FDA and most commercial labs structure a test when a lot or run is submitted, not a requirement that every production batch be tested. There’s no FDA mandate dictating how often a maker must test; many potters test when they introduce a new glaze, clay body, or firing schedule, and periodically thereafter, as a due-diligence practice rather than a legal obligation enforced batch-by-batch.
Why do mugs and pitchers have a stricter limit than bowls?
Cups, mugs, and pitchers are used with hot coffee/tea or acidic juice for extended contact time, which increases how much lead or cadmium can leach out. The FDA set their limit at 0.5 µg/mL — well below the limits for flatware or general hollowware — to account for that heavier real-world exposure.
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Photo: Windmemories / CC BY-SA 4.0, via Wikimedia Commons.