{"id":6648,"date":"2026-11-06T10:30:00","date_gmt":"2026-11-06T10:30:00","guid":{"rendered":"http:\/\/kmceramic.company\/en\/ceramic-mug-lead-test-failure-causes\/"},"modified":"2026-11-06T11:39:18","modified_gmt":"2026-11-06T11:39:18","slug":"ceramic-mug-lead-test-failure-causes","status":"publish","type":"post","link":"https:\/\/kmceramic.company\/fr\/ceramic-mug-lead-test-failure-causes\/","title":{"rendered":"Why Ceramic Mugs Fail Lead and Cadmium Tests"},"content":{"rendered":"

Compliance & Certification<\/span> ceramic-mug-safety-certifications<\/a><\/p>\n

Most lead failures on ceramic mugs are not a body problem. The clay is rarely the source; the failure usually sits in the decoration layer or the overglaze, and it appears on specific colours rather than across the whole order. Knowing which colours and which firings cause it lets you fix the batch instead of scrapping it.<\/p>\n

\"Ceramic
<\/figcaption><\/figure>\n

Where the lead actually sits<\/h2>\n

A ceramic mug is body, glaze and decoration. The body is fired at 1,180 to 1,300 degrees and the metal oxides in the clay are locked into the matrix, so extraction from the body is negligible. The glaze is a glass layer, and a well-fired glaze at 0.25 to 0.35 mm is chemically stable. The decoration is the weak point: overglaze decals fire at 750 to 850 degrees, well below the glaze maturation point, so the pigment sits on the surface rather than inside the glass.<\/p>\n

The colours that fail most<\/h2>\n

Cadmium is a pigment in reds, oranges and deep yellows, and lead is a flux in low-fire enamels and in some gold and platinum lustres. In practice, a mug with a red logo and a white body will fail more often than the same mug with a blue logo. Gold and platinum decals are the second common source: the metallic film is thin and can be abraded in the dishwasher, releasing the metals underneath.<\/p>\n

Recycled frit and batch drift<\/h2>\n

Glaze frit is bought in batches, and cheaper frit sometimes carries lead as a contaminant from recycled glass. A factory that changes frit supplier between orders can pass one test and fail the next with no change to the recipe on paper. That is why the fired chip and the frit batch number matter as much as the test report.<\/p>\n

How the test is run<\/h2>\n

A typical extraction test uses 4 percent acetic acid at 70 degrees for 24 hours, and the result is reported per unit area or per litre depending on the market. A result that is 20 percent under the limit is not a pass with margin; it is a batch that will fail when the kiln drifts. Treat anything within 30 percent of the limit as a warning.<\/p>\n

Fixing it without scrapping the batch<\/h2>\n

Three routes work. Change the pigment to a lead-free and cadmium-free system and refire the decoration, which usually costs 0.03 to 0.08 per unit. Add a barrier glaze over the decal, which seals the pigment but changes the surface feel. Or move the artwork into the glaze layer (in-glaze decoration) at 1,100 degrees, which is the durable answer but needs a minimum run and a longer lead time.<\/p>\n

What to write in the specification<\/h2>\n

Name the pigment system, the firing temperature of the decoration, and the extraction limit with the test method. Require a report per frit batch rather than per year. And keep a fired sample with the decoration applied, because the report describes a batch and the sample describes what you will actually receive.<\/p>\n

What a test costs and how long it takes<\/h2>\n

A food-contact extraction test costs 80 to 220 dollars per article per colour set and takes 5 to 7 working days at a Chinese lab, 10 to 15 at a European one. Testing one white mug is cheap; testing eight colours across three shapes is 1,500 dollars and a month. That is why factories test the pigment system rather than every SKU, and why the report you receive usually covers a representative article.<\/p>\n

A decision tree for a failed batch<\/h2>\n

When a result comes back over the limit, work in this order. First, identify which colour failed: if it is red, orange or yellow, the cadmium pigment is the suspect. Second, check the decoration firing temperature; anything under 780 degrees is a low-fire film. Third, ask for the frit batch number and compare it to the batch that passed. If the failure is one colour on one batch, refire with a lead-free pigment at 0.03 to 0.08 per unit. If it is every colour on every batch, the glaze itself is the source and the frit has to change.<\/p>\n

What the number means for a retail buyer<\/h2>\n

A retail buyer reads the report differently from an importer. The importer needs a pass; the retailer needs a pass with margin, because their own lab will retest on arrival and a failure there means a recall rather than a rejected shipment. That is why a result within 10 percent of the limit is treated as a fail by most retail compliance teams, even though it is legally a pass.<\/p>\n

A note on gold and platinum decoration<\/h2>\n

Metallic lustre is the decoration that most often escapes scrutiny, because the visual value is high and the order quantity is small. A gold rim on a mug is fired at 750 to 800 degrees as a thin film, typically under 0.1 micron, and that film abrades in a commercial dishwasher within 100 to 150 cycles. Once abraded, the metals in the lustre are exposed to food contact. If a brand wants a gold rim, specify a barrier glaze over it and test the finished piece rather than the base mug, because the decoration is applied after the body has already passed.<\/p>\n

Test the Decoration, Not Just the Body<\/h2>\n

Lead failures live in the decoration layer: red and orange pigments, low-fire overglaze, gold lustre and contaminated frit. Fix the pigment system, add a barrier layer or move the artwork in-glaze, and require a report per frit batch so the next container matches the one that passed.<\/p>\n

Related: ceramic mug range<\/a> \u00b7 safety certifications guide<\/a>.<\/p>\n

\"Ceramic
<\/figcaption><\/figure>\n
\n

More in this series: Compliance & Certification<\/p>\n