Ceramic / Stoneware / Porcelain

Lead and cadmium have long been used in glazes and overglaze decoration - lead for a smooth glassy finish that lets colour show through, cadmium for bright reds, oranges and yellows - and both can leach into food. FDA sets action levels measured by a 24-hour acetic acid leach test (ASTM C738) on six units: for lead, 3.0 micrograms/mL averaged across six for flatware, 2.0 for small hollowware, 1.0 for large hollowware, and 0.5 for cups, mugs and pitchers; for cadmium, 0.5 for flatware and small hollowware and 0.25 for large hollowware. No FDA regulation authorises lead as a component of foodware at all, decorative ceramicware that fails must carry a "Not for Food Use" label under 21 CFR 109.16, and Import Alert 52-08 covers imported ceramicware for lead and cadmium. California's tableware law and Prop 65 add a warning requirement on top. In practice the risk concentrates in a short list: traditional glazed terracotta from Latin America, highly decorated traditional Asian ware, hand-crafted pieces with unknown glazes, antiques predating the rules, and any piece whose glaze has gone dusty, chalky or corroded. Plain white dishes rarely contain lead, and CDPH notes tableware is a minor lead source for most people compared with paint and soil - but it is not a negligible one for children and pregnant women using the wrong piece daily. See the lead-safety rating on individual products for how we score this.

A well-vitrified glazed body handles oven and microwave heat without chemically changing, and it is a poor conductor, so it heats slowly and holds heat once hot - the reason ceramic drippers and baking dishes work. It is thermal-shock sensitive: a cold dish into a hot oven or a hot dish onto a wet surface cracks it, and repeated cycling crazes the glaze into a fine web of cracks. Heat also drives leaching where lead is present, so CDPH advises against cooking, microwaving or storing food in any piece whose glaze you are unsure of, and against acidic foods in particular.

Turn the piece over: the unglazed foot ring shows you the clay body, and porcelain will glow translucent when the rim is held against a light while stoneware and earthenware will not. Run a finger over any decoration - if it feels raised or rough, or you can see brush strokes standing above the glazed surface, it is overglaze decoration, which is where lead and cadmium concentrate; decoration under a clear glaze is far safer, and decoration on the outside below the rim is not a food-contact path at all. Do not confuse fired ceramic with a sprayed sol-gel "ceramic coating" on a metal pan, which is a different material entirely and has its own page. Ask a brand two questions: does this piece meet California Proposition 65 tableware limits, and can you provide the leach-test results for lead and cadmium. Note that "lead-free" and "lead-safe" are not the same claim: lead-safe means it contains lead but releases less than the legal limit.

Chips and cracks are the normal end, and both matter beyond looks: a crazed or chipped glaze exposes more surface, harbours residue, and increases lead release where lead is present, though CDPH is clear that leaching happens through intact glaze too. Dishwashers can etch and dull a glaze over years and will accelerate lead release from a leaded one, which is one argument for hand-washing anything of uncertain provenance. A sound modern piece from a production maker lasts decades.

Fired ceramic is not recyclable in any normal sense - it will not remelt with container glass and a single broken mug can contaminate a glass load, so it belongs in the trash, where it is inert and permanent. Some construction aggregate programs take clean rubble. The useful move is upstream: intact dishware is easy to donate or resell, so reuse rather than recycling is the realistic path.