Food Safety
Whether a pot is safe to eat from is a property of the whole fired system — body, glaze, fit and firing — and, the moment you sell, a legal question too. This page collects the studio knowledge: which ware and firing types carry risk and why, how to pre-check at home, and where accredited testing and the law come in for Germany, the EU, the US and the UK.
Everything here is educational guidance for studio potters — compiled with care, without warranty. Regulations change, differ by country, product and audience, and only the current official texts count. Before selling functional ware, confirm the requirements with the competent authority or an accredited laboratory.
A crazed glaze over a porous body wicks liquid into the crack network, where residues and bacteria sit beyond any sponge. On fully vitrified porcelain it is mostly cosmetic; on earthenware it disqualifies the surface for food.
Low-fired, porous, deliberately crazed and loaded with carbon — the surface cannot be sanitized. Raku is decorative ware, full stop: use it for everything except food and drink.
Unglazed, low-fired, sealed at best with wax or oil: it absorbs whatever touches it. Never for food — even as a vase it wants an inner vessel.
Fine for food when fully covered by a stable, well-fitted glaze — but the body underneath stays porous: chips, dry foot rings and crazing open it up. Inspect regularly, retire damaged pieces.
A glaze fired below maturity never built its full glass network: it stains, marks and leaches. If the cone did not fall, the piece is not food-ready yet — refire it.
Vitrified stoneware or porcelain under a stable, mature, well-fitted glaze free of leachable heavy metals. This is what dishwasher-grade tableware is made of.
Leave a lemon slice or vinegar on the glaze overnight. Any change in color or gloss means the surface is reacting — treat it as leaching until a lab says otherwise.
Weigh a dry fired shard, soak it 24 hours, weigh again. Much more than about 2 % weight gain means the body is not vitrified — glaze fit has to do all the sealing.
Ink or strong tea wiped over the glaze reveals crack networks the eye misses. Any crazing over a porous body moves the piece to decorative duty.
Run a candidate piece through repeated dishwasher and microwave cycles before selling the form: fit faults like crazing and shivering often appear only after thermal cycling.
Framework Regulation (EC) 1935/2004 covers everything that touches food; the Ceramic Directive 84/500/EEC sets migration limits for lead and cadmium, tested by a 24-hour soak in 4 % acetic acid. Sellers need a declaration of compliance. A revision with far stricter limits and more metals has been in the works — check the current state before selling.
The EU rules apply via the Bedarfsgegenständeverordnung under the LFGB. Whoever places tableware on the market is responsible for compliance; the state food-control authorities enforce it. Testing: DAkkS-accredited food-contact laboratories — many offer small-batch ceramic migration tests.
The FDA sets action levels for lead and cadmium in ceramicware, checked with standardized leach tests (ASTM procedures); ware on the market can be sampled. California's Proposition 65 adds far stricter warning thresholds. Testing: accredited labs run the FDA-protocol leach tests.
The EU-derived regime was retained: the Materials and Articles in Contact with Food regulations keep the lead and cadmium limits. Guidance comes from the Food Standards Agency and local Trading Standards; testing via UKAS-accredited laboratories.
Children's ware, ovenware and rims for drinking are judged more strictly than flatware — say what a piece is for, and test for that use.
Related: material cautions on the Glazing page · firing methods overview