The "Lead-Free" Mugs Failed for Cadmium at Import
Ceramic Tableware Lead & Cadmium Test Guide
Hello, this is StartMade.
A brand selling kitchenware online had a ceramics factory in Fengxi (枫溪), Chaozhou (潮州), Guangdong, make a set of mugs and plates. The design used red and orange floral decals, and the spec sheet said "lead-free glaze, compliant with food contact standards." The factory sent an approved sample along with a lead and cadmium release test report, and the first 2,000 sets passed the import inspection without a problem. Sales were good, so four months later the brand reordered 5,000 sets. At pre-shipment inspection, dimensions, chips and color all passed.
The trouble came after the reorder reached the Korean port. The mugs were picked for a random check at import declaration, cadmium release exceeded the limit, and the shipment was ruled non-compliant: return it or destroy it. Leftover samples went back to the lab, and the problem turned out to be the floral pattern on the rim, right where lips touch the cup. Only later did the brand learn that the factory had switched decal suppliers for the reorder and lowered the decal firing temperature to save on gas.
Lead and cadmium in ceramic tableware are tricky because you cannot see them at all. A lead glaze shines just like a lead-free one, and a red made with cadmium pigment is often even brighter. Release levels show up only after the piece sits in an acid solution for a day, and the same glaze can give different results depending on firing temperature. This post covers where lead and cadmium come from, the limits of each check, gaps in test reports, common supplier substitutions, and what to check in the spec sheet and at inspection.
One line saying "lead-free glaze" and a sample test report are not enough. Set release limits and test methods by product type, decoration method and a no-decoration zone at the rim, glaze and decal suppliers and firing temperature in the spec sheet, and run release tests on samples you pick yourself from production to prevent import rejections and recalls.
1. Where Do Lead and Cadmium in Ceramics Come From?
The ceramic body itself rarely releases lead. Most problems come from the glaze covering the surface and the decoration applied on top. Lead helps glaze melt at lower temperatures and boosts gloss, so it still turns up in cheap glazes. Cadmium is used in pigments for bright reds, oranges and yellows. Once properly melted and locked inside the glassy layer, they barely leach, but if the piece is underfired or the decoration sits exposed on the surface, acidic foods like vinegar or tomato sauce can dissolve them.
That is why how the decoration was applied matters even for the same design. Decoration placed on top of the glaze and refired at a low temperature gives vivid color but stays exposed on the surface. Decoration sunk into or under the glaze at high temperature offers fewer color choices but much lower release risk.
| Decoration | Firing | Release risk | Notes |
|---|---|---|---|
| Overglaze (釉上彩) | Decals or paint on the glaze, refired at roughly 700-850°C | High | Widest color range and lowest cost, especially risky on the rim |
| In-glaze (釉中彩) | Applied on the glaze, fired at roughly 1,100-1,250°C so it sinks into the glaze | Low | Smooth surface and good durability, somewhat higher cost |
| Underglaze (釉下彩) | Painted on the body, covered with glaze and fired at high temperature | Very low | Limited colors, traditional styles such as blue-and-white |
| Colored glaze (色釉) | Pigment mixed into the glaze itself | Depends on formula and firing | Low-fire colored glazes often contain more lead |
| Gold or silver rim (金边) | Precious metal paint, refired at low temperature | Medium | Not microwave safe, the base paint sometimes contains lead |
Overglaze is not bad by definition. With lead-free, cadmium-free decals and enough firing temperature, it can meet the limits. The problem is when the decals, glaze or firing conditions in production differ from the approved sample. Importing food contact products in general is covered in Episode 64.
2. Checking Methods — From Quick Kits to Release Tests
Ask "无铅的吧?" and the factory almost always answers "都是无铅釉，有报告" (it's all lead-free glaze, we have a report). Before you accept the report, decide how you will check.
| Method | How | What it shows | Limits |
|---|---|---|---|
| Visual and touch check | Run a fingertip over the decoration and check where rim decoration sits | Whether it is overglaze, decoration in the lip area | Says nothing about lead or cadmium levels |
| Quick lead test kit | Rub the surface with a reagent swab and watch for color change | Rough presence of lead exposed on the surface | Misses cadmium, and easily misses lead inside the glaze or at low levels |
| Handheld XRF | Measures surface element content by X-ray fluorescence | Lead and cadmium content in glaze and decoration, lot-to-lot comparison | Content, not release; a well-fired lead glaze can have high content but low release |
| Release test | Fill or soak with 4% acetic acid for 24 hours at room temperature, then analyze the solution | Confirms compliance with regulatory limits | Takes time and money, needs samples |
| Firing record check | Compare kiln temperature records and firing time | Flags likely underfired lots | Records can be faked |
| Wash durability test | Repeated dishwasher cycles, then recheck decoration and release | Whether release rises with use | Long and costly |
Use XRF as a Screen
Handheld XRF gives results in seconds, which makes it handy at inspection. Measure the approved sample as a baseline, and if lead or cadmium readings jump in production, send that lot for a release test. Just do not pass a lot because XRF is low or fail it because XRF is high. Regulatory limits look at how much leaches into food, not at content.
Order Release Tests by Product Type
Release limits differ for flat pieces like plates, small bowls, large bowls, cups and cookware. If you simply ask a lab for "ceramic lead and cadmium testing," it may test against the loosest category, so tell the lab which category applies to each product in advance. Some standards also test the cup rim separately. How to read test reports is covered in Episode 10.
3. What Are the Typical Criteria?
Here are approximate values commonly used for quality control. Units and categories vary by country and are revised often, so confirm the actual criteria for your market with a lab.
| Product type | Lead (approx.) | Cadmium (approx.) | Notes |
|---|---|---|---|
| Flatware (depth under 25mm, like plates) | 0.8mg/dm² or less (ISO 6486-2, EU) | 0.07mg/dm² or less | Measured as release per area |
| Small hollowware (bowls) | 2.0mg/L or less (ISO 6486-2), EU 4.0mg/L | 0.3mg/L or less | Capacity under 1.1L |
| Large hollowware and storage | 1.0mg/L or less, storage 3L and up 0.5mg/L | 0.25mg/L or less | Stricter for longer storage |
| Cups and mugs | 0.5mg/L or less (ISO 6486-2, US FDA) | 0.25mg/L or less | Some standards test the lip area separately |
| Cookware | Roughly 0.5mg/L or less | Roughly 0.05mg/L or less | Stricter for ware placed directly on heat |
| California Prop 65 | Separate limits far below the above | Separate limits | Check whether a warning is required for US sales |
The cup limits are much stricter, so the plates in a design can pass while only the mugs fail. If you order sets, it is safer to choose decals and glaze to meet the strictest item. The Korean import declaration process is covered in Episode 89.
4. Why You Cannot Take Release Test Reports at Face Value
Ask for lead-free proof and the factory usually sends a release test report (检测报告) from a testing body or a lead-free statement from the glaze supplier. These documents have gaps.
| Gap | What happens | What to check |
|---|---|---|
| Factory-picked samples | The report covers samples the factory chose itself, so you cannot tell if production matches | Who picked the samples, whether a third party sampled at random |
| Report on plain ware | A report on undecorated white ware is used for decorated products | Whether the report photo and item number match the actual design |
| Wrong category | A report tested to flatware limits is used to cover mugs too | Category and limits for each item |
| Old reports | Reports from one or two years ago are reused | Look up the issue date and report number on the testing body's site |
| Glaze supplier statement | Only says the glaze material is lead-free, not that the finished product passes | Release test report on the finished product |
| Wrong market | Only Chinese GB reports, no testing to Korean, US or EU limits | State the target market's standard and test method |
5. Common Supplier Substitutions
With ceramic tableware, a change in glaze or decals barely shows on the outside. When price pressure comes, factories cut corners first on the raw materials and firing nobody can see. These are the types we have actually run into in our consulting work.
| Type | How it works | How to prevent it |
|---|---|---|
| Lead-free for samples only | Approved sample uses lead-free glaze and branded decals, production uses cheap materials | Fix glaze and decal supplier names and item numbers, require purchase invoices |
| Decal supplier switch | Moves to a cheaper decal (花纸) supplier for the reorder | Prior written approval for any decal supplier change, lot-by-lot XRF comparison |
| Lower firing temperature | Cuts refiring temperature or time to save on gas | State firing temperature and time, require kiln records |
| Moving the decoration | Shifts the design up toward the rim to "look better" | Mark the no-decoration rim zone on the drawing |
| Low-fire colored glaze | Uses an easier low-fire colored glaze instead of a high-fire one | State glaze type and firing temperature |
| Outsourcing | Hands only decoration and refiring to another workshop | Fix the workshop for each process, ban unauthorized outsourcing |
The most common is switching decal suppliers on a reorder. Ceramics factories rarely make their own decals and buy them from nearby printers, so moving to a cheaper printer leaves no visible trace. A process requiring prior approval for material or process changes is covered in Episode 119.
6. The Cost of Exceeding Lead and Cadmium Limits
Release problems stay hidden, then surface all at once at customs, in a market check or through a customer complaint, and the damage spreads far beyond the cost of the product.
- Import rejection: Food contact products are inspected at import declaration. If they fail, the shipment must be returned or destroyed, and you absorb the freight, storage and disposal costs.
- Tighter inspection: After one failure, the same manufacturer and item face detailed inspection for a while, adding time and cost to every clearance.
- Sales stop and recall: If products already sold exceed the limits, a sales stop and recall order can follow, and listings come down from platforms.
- Brand trust: One headline saying "heavy metals found in a child's rice bowl" casts doubt on every other piece of tableware the brand sells.
Recalls and product liability are covered in Episode 53, and claims and disputes in Episode 36.
7. What to Put in the Spec Sheet
Every factory reads "lead-free glaze" differently. Put the items below in a table and attach it to the spec sheet.
| Item | Example |
|---|---|
| Applicable standard | Compliance with the target market's standard (e.g., Korean MFDS ceramic requirements, ISO 6486-2, US FDA), category stated for each item |
| Glaze | Lead-free glaze, glaze supplier name and item number fixed, no low-fire colored glaze |
| Decoration method | In-glaze, or overglaze with lead-free and cadmium-free decals, decal supplier fixed |
| No-decoration zone | Within 20mm of the rim on cups and teacups, and the food-contact inner surface of plates and bowls where needed |
| Firing conditions | Main firing and refiring temperature and time, kiln records kept |
| Outsourcing | Workshops for decoration and refiring fixed, no unauthorized outsourcing |
| Documents | Release test reports by item and design (issued within 6 months), glaze and decal purchase invoices, XRF readings per lot, kiln records |
Writing the glaze and decal suppliers into the spec sheet is a hassle, but it is essential. The actual release results depend on those two suppliers' materials and the firing conditions, not on the factory name. How to write a spec sheet and BOM is covered in Episode 59.
8. Adding Lead and Cadmium Checks to Your QC Checklist
Sample Stage
When the approved sample arrives, pick samples for each item, send them for release testing to your market's standard, and measure the same pieces with handheld XRF to record a baseline. Note the glaze and decal supplier names and item numbers too. Seal the approved sample with the date and item number so you can compare against it later. Sample management is covered in Episode 34.
Production Stage
Ask for the purchase invoices and photos of the packaging labels on the day decals and glaze arrive at the factory. Check that supplier names and item numbers match what you approved and that refiring kiln temperature records match the spec. If workshop photos show decals from another supplier piled up, ask about them on the spot. Production tracking is covered in Episode 102.
Pre-Shipment Inspection Stage
The inspector picks packed products personally, measures the decorated areas with XRF, and checks where rim decoration sits and the condition of the decorated surface. If readings differ sharply from the approved sample, seal randomly picked samples and send them to a third-party lab for release testing. Ceramics can also crack under sudden temperature changes, so it is worth adding a thermal shock test. Pre-shipment inspection is covered in Episode 100, and thermal shock testing in Episode 147.
9. Sample Request Wording for the Factory
Putting the wording below in your PO or spec sheet takes glaze and decoration out of the factory's discretion and makes it easier to assign responsibility if problems arise.
"本产品所有接触食品的陶瓷部件须符合销售国食品接触材料标准（韩国食药处陶瓷制品标准及ISO 6486-2），铅、镉溶出量按产品分类分别检测。须使用无铅釉，不得使用低温色釉。贴花须使用无铅无镉花纸，釉料及花纸供应商和型号须与确认样一致，如需更换须提前书面确认。杯类口沿向下20mm范围内不得有釉上彩装饰。烤花温度及时间须按约定执行并保留窑炉记录，装饰及烤花工序不得外发。每批釉料及花纸入厂时提供采购单据及标签照片，每批留存XRF检测数据。出货前由我方随机抽取成品封样送第三方检测，如不合格，整批重做或退货，费用由供应商承担。"
(All food-contact ceramic parts must meet the target market's food contact standards (Korean MFDS ceramic requirements and ISO 6486-2), with lead and cadmium release tested by product category. Lead-free glaze must be used, and low-fire colored glaze is not allowed. Decals must be lead-free and cadmium-free, and the glaze and decal suppliers and item numbers must match the approved sample; any change requires prior written approval. No overglaze decoration within 20mm below the rim of cups. Decal firing temperature and time must follow the agreed terms with kiln records kept, and decoration and decal firing may not be outsourced. Purchase documents and label photos must be provided each time glaze or decals arrive, and XRF data kept for every lot. Before shipment, we will randomly pick and seal finished products for third-party testing. If they fail, the whole lot will be remade or returned at the supplier's cost.)
10. Three Real Cases
These are anonymized versions of patterns we see often in consulting. Amounts and figures are examples.
Case 1 — Floral Mug Set
This is the case from the start of this post. When the brand pushed back with the test results, the factory held its ground, saying "the sample report shows a pass." A second look at the report showed the sample was a plate the factory had sent itself, and no mug had been tested. Only then did it come out that the factory had switched decal suppliers for the reorder and lowered the refiring temperature. Because the spec sheet said only "lead-free glaze" and set no item-level limits, decal supplier or rim no-decoration zone, the brand absorbed much of the return cost and inventory loss.
Case 2 — Children's Tableware Set
A company importing children's tableware found at pre-shipment inspection that XRF readings on bowls with a yellow colored glaze were several times higher than the approved sample. The answer was that the high-fire colored glaze they had been using gave uneven color, so they switched to a low-fire one. Release testing showed cadmium close to the limit, and the company halted shipment and had the lot remade. Since then it has written the colored glaze type and firing temperature into the spec sheet and receives XRF values for every lot.
Case 3 — Gold-Rimmed Teacups
A seller importing gold-rimmed teacups for cafes was asked by a US buyer for testing to California Prop 65. It had only Korean and Chinese standard reports, and lead was found in the base paint under the gold rim, meaning the cups could not be delivered without a warning label. Stating the target market in the spec sheet from the start and testing to that standard would have prevented this.
11. Common Mistakes
- Passing products on the factory's sample test report alone
- Assuming a plate report also clears mugs and bowls
- Believing the reorder would match because the first shipment cleared customs
- Concluding a piece is safe because a quick lead kit did not change color
- Passing or failing lots on XRF readings alone
- Accepting only Chinese standard reports without setting the target market's standard
12. Ceramic Tableware Lead and Cadmium Checklist
Spec Stage
- Stated the target market's standard and the category for each item
- Stated lead-free glaze and no low-fire colored glaze
- Set the decoration method and lead-free, cadmium-free decals
- Marked the no-decoration rim zone on cup drawings
- Stated refiring temperature and time
- Fixed glaze and decal suppliers and set a change approval process
Sample and Production Stage
- Release tested approved samples per item and set XRF baselines
- Sealed and stored the approved sample with the date and item number
- Received purchase invoices and label photos when decals and glaze arrived
- Checked that report sample photos and item numbers match the actual design
- Cross-checked refiring kiln records
Pre-Shipment Inspection Stage
- Measured decorated areas of randomly picked finished products with XRF
- Checked rim decoration position and decorated surface condition
- Sealed random samples and sent them to a lab for release testing
- Checked the reorder to the same standard as the first shipment
Wrapping Up - Check Release Numbers, Not Glaze Shine
Mugs leaving the factory shine the same whether the glaze is lead-free or not, and the floral pattern is sometimes even brighter on cheap decals. The difference shows up at customs or on the customer's table, and by then the whole shipment is tied up. Writing item-level release limits, glaze and decal suppliers, a no-decoration rim zone and firing conditions into the spec sheet, and testing samples from every lot, costs far less than the returns, disposal and recalls you would pay for later.
There is also something you can do right now. Ask the factory currently in production for its glaze and decal supplier names, recent purchase invoices, item-level release test reports and refiring kiln records. If the only answer is "都是无铅的，放心" (it's all lead-free, don't worry), build a ceramic tableware control sheet and send it before your next order.
StartMade supports you on the ground with spec sheets that set the target market's standard and item categories, glaze and decal supplier and invoice checks, incoming material checks during production, and pre-shipment inspection with sealed samples sent to a lab. If you have already had an import rejection, we start by testing the remaining stock; if you are preparing new tableware, we start with the spec sheet together.
Is Your Ceramic Tableware the Lead-Free Product on Your Spec Sheet?
From setting item-level release limits to glaze and decal supplier checks, decoration and firing record checks, lab analysis and pre-shipment inspection
We check on the ground before an import rejection happens