Vintage Libbey glass with orange, brown & yellow floral pattern: 87,100 ppm lead by XRF

XRF readings:
Lead: 87,100 ppm · Cadmium: 3,541 ppm · Arsenic: not measured
Verdict: Extreme, do not use + High cadmium
87,100 ppm lead, roughly 8x the CPSC 90 ppm children's limit. At this concentration, even fired ceramic glaze carries leaching risk under acidic food conditions. No food contact under any circumstances. FluoroSpec will glow. NOTE: 3,541 ppm cadmium also detected, a separate and serious concern for colored glazes.
There is no safe amount of lead. This number is a starting point, not a verdict on your safety. What matters is whether the lead can actually reach a person. Think of tacks: a box of them in a drawer is fine, the same tacks loose on the kitchen floor are not. Lead locked in a stable fired glaze is mostly in the drawer. The same ppm in something a child can mouth, chew, or swallow, like paint dust, play sand, or a worn or chipped surface, is on the floor. Food is its own category: if the lead is in something you eat or drink there is no "might reach you," you are guaranteed to take the dose. Dose is what counts: 1 gram of a 90 ppm material is about 90 micrograms of lead, roughly 40 times the 2.2 micrograms per day the FDA uses as a child reference level. A reading that looks low can still matter in the wrong form, and a high reading on intact glaze may never reach anyone. Do not trust the number alone. Test the actual item, and when in doubt keep it away from kids and food.

What XRF actually measures (and what it doesn't)

XRF detects elemental lead presence on the surface. It does not measure whether that lead migrates into food. Those are different questions. Lead bound in fired ceramic glaze is chemically locked in the vitreous matrix and, in independent leach testing on items up to ~3,000 ppm, showed no detectable migration. Lead in surface paint, decals, or worn glaze behaves very differently and is a meaningful exposure risk.

What this XRF reading actually means →

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Source data: independent consumer-safety researcher (factual data; verdict by EverythingLead)
Original source: https://tamararubin.com/2021/07/vintage-libbey-glass-with-orange-brown-yellow-floral-pattern-87100-ppm-lead-3541-ppm-cadmium-in-the-painted-decorations/
Test method: XRF (Niton XL 5 Plus, 1.5 sigma)
License: Factual XRF measurements are not copyrightable (Feist v. Rural Tel., 499 U.S. 340). Verdict and methodology CC-BY-SA 4.0.