Department of the Environment and Heritage
Lead glazes used in ceramic ware can be a health hazard, affecting the intellectual development of young children. Poisoning can occur if the lead leaches into your food or drink.
Use of lead glazes
Lead glazes are most commonly used on earthenware, and on older bone china and porcelain. They are reliable, easy to control, durable for most purposes and they produce attractive glazes.
When the glazes are properly formulated and fired at a high temperature, the lead is sealed. However, if they are not properly prepared and fired, lead may leach (i.e. move from the glaze) into food stored in or on the ceramic ware.
The degree of lead leaching from tableware can vary. It depends on how often the tableware is warmed and used, and the amount of contact it has with food and drink. Cups and bowls are of greater concern than dishes. Acidic foods will accelerate any leaching.
These days, raw or free lead is rarely used. The lead is compounded with silicate into a frit, which is less dangerous. In catalogues, manufacturers label the glazes containing lead and use terms such as lead-free, non-toxic and dinnerware-safe to identify lead-free glazes.
However, it is worth checking your kitchen to identify risky items and to ensure their use does not create health hazards.
Risky ceramic ware
Ceramic ware with a corroded glaze is extremely dangerous and it should never be used to serve food or drink. It is easy to see corroded glaze because it has a chalky-grey residue that is present after the item has been washed.
Old tableware, especially imported items, homemade or handcrafted china should be treated cautiously. Testing is recommended.
Highly decorated ceramic ware is of concern because of the high lead levels that are typically found in brightly coloured glazes. Be wary of highly coloured glazes on inside surfaces that could have contact with food or drink, as the potter might not have anticipated that the item would be used in this way when applying the glaze.
Decorations on top of the glaze may present a health hazard. The decoration is on top of the glaze if you can feel it when you rub your fingers across the ceramic ware or if you can see the brush strokes of the decoration above the glazed surfaces.
What to do to reduce the risks
Ceramic ware and glazes that are risky should not be used to store food or drink. The longer the food is in contact with such glazes, the more the lead will leach into it.
Highly acidic foods (for example citrus juices, apple or tomato juice, cola, salad dressings, vinegar, coffee, tea and tomatoes) should not be served in questionable china.
Questionable china should not be used daily. Be wary of old coffee mugs, cheap, imported china and ceramic containers. Heating or microwaving questionable china should be avoided. Heat can accelerate the lead-leaching process. Reheating coffee in an old mug in the microwave is a particularly risky thing to do.
Testing for lead
Small test kits available from some paint wholesalers and hardware stores can test ceramic ware for lead. The instructions are on the packet. The only drawback is that overseas experience with many of these test kits suggests that false negative and false positive results may occur.
As an alternative, there is also an Australian Standard for testing the amount of leachable lead in ceramic ware. This test is reliable, but it requires samples to be sent to a laboratory for analysis.
If you have any doubts about your ceramic ware, don’t use it.
Other sources of lead in food
Lead from a number of sources can contaminate food. Some of these include soil, air-borne lead dust, fertilisers, leaded crystal, pewter mugs and food cans.
Leaded crystal may contain anywhere between 14% and 36% lead oxide. Spirits kept in crystal decanters for a long time can become heavily contaminated.
Lead solder was once widely used to seal canned foods. Now nearly all cans produced in Australia are welded. Imported cans with lead solder are checked for lead contamination, but it is worth avoiding acidic foods that are imported in soldered cans, particularly if the cans appear to be old.
Lead glazes are prohibited from use on commercial dinnerware in Australia. They are permitted on decorative ceramic ware only.
For more information:
Phone the Department of the Environment and Heritage's Community Information Unit on 1800 803 772.
You can ask for fact sheets on lead in the environment, lead lighting, pottery and house, automobile and marine paints.
See also our website at http://www.environment.gov.au/settlements/chemicals/index.html.