XRF vs leach testing: two different questions

Last reviewed July 2026.

A recurring collision in cookware content: a blogger's XRF gun reads lead in a pan, the brand points to passing lead tests, and both sides call the other liars. Usually, nobody is lying — they're answering different questions.

XRF: what's in the material

X-ray fluorescence instruments identify the elements present in whatever they're pointed at, down to trace levels. It's the right tool for "does this object contain lead anywhere in its matrix?" — and hobbyist XRF surveys of cookware (Tamara Rubin's Lead Safe Mama project is the best-known) have flagged metals in enamel bodies, glaze pigments, even 100%-ceramic pans that pass every leach test. An XRF hit tells you an element exists in the material. It does not tell you whether any of it can reach your food.

Leach testing: what reaches the food

Exposure-relevant testing simulates use: the standard methods (FDA's compliance procedure for glazed surfaces, ASTM C738; ASTM C872 for porcelain enamel) hold a 4% acetic-acid solution — think boiling vinegar — against the cooking surface for a set time, then measure what migrated into the liquid. This is the number FDA compliance, California Prop 65 leach standards, and every food- contact regulation actually regulate, because it approximates a worst-case meal, not the pan's elemental inventory.

Both can be true at once

A pigment can contain cadmium that is fully vitrified — locked in glass — and never migrates: detectable by XRF, absent from the leachate. Le Creuset's position is exactly this shape: cadmium pigments only in bright exterior colors, behind an anti-acid barrier, with food-contact interiors in sand/white/black enamel (our row). Xtrema is the documented case: hobbyist XRF found metals in the ceramic body, while both its published SGS leach results and an independent EPA-certified-lab acid-bath test (commissioned by Mamavation) measured lead migration orders of magnitude below California's warning threshold.

Which one should you care about?

For "will this pan put lead in my dinner", leach data answers the question; XRF raises it. XRF surveys are genuinely useful — they're how worn, chipped or vintage items get flagged, where the vitrification argument stops applying (damaged enamel exposes what was locked away). A fair reading: XRF finds candidates; leach tests deliver verdicts; damage reopens the case.

How we use each

In our table, only published leach/migration results and PFAS analyses count toward a verified verdict. XRF findings never mark a claim contradicted — they answer a different question — but where notable ones exist, the brand row says so and links them, because you deserve both facts and the distinction.

See who publishes real leach data →

We do not test cookware — we index published third-party results and public records, with attribution, and make no health claims.