Pottery/Ceramic and Bone China from China
QUESTION: I read your reply to a question about glazes on Chinese tableware. You warned about glazed porcelain or stoneware from China. I am not familiar with various designations for tableware, but there are mugs for sale referred to as ceramic, and some bone china. If ceramic and bone china are manufactured in China, are they also likely to be toxic?
Mugs are also available made of frosted glass. Perhaps this is outside your expertise. I wonder if glass mugs made in China would be safe?
ANSWER: Dear Maggie,
Thank you for your recent question. When that article was written, there had been a scare with children's toys having lead and other toxic materials in the making of the item from China. Pottery ware too has the same conditions concerning toxic materials when they are imported from China. However, the FDA has curtailed much of the concern through testing and federal law requirements to halt the importation of these items into the United States.
What we are mainly concerned with now are the existing items that were brought into the United States prior to regulation. In December 2012, the FDA released guidelines and regulations concerning the importation of foodware to the United States. These documents contain information on how foodware is regulated and what methods are used to control the safe importation of foodware from China, including a list of what the FDA considers to be safe manufacturers in China. However, problems do still exist.
One of the requirements for identification of safe foodware coming from China is an emblem on the box containing the foodware. An item is removed from the box and tested for abrasion defaults. If the item fails, it is sent to the lab for further leach testing and chemical analysis. If the item passes, the whole box is considered safe.
This is where the regulations fall short. Unless all items are checked, risks of non-checked items being safe are very high as foodware items containing lead or cadmium may still bypass inspection. True also is the fact that, although the box the foodware comes in is labeled with an emblem for identification of safe manufactures, because of the above shortfall and the fact that no item is required to be marked safe along with the manufacturers emblem on the bottom of the foodware, the unknowing consumer has no way to identify safe foodware items from non-safe foodware items, with the exception of carrying around the list of safe manufacturers to cross identify or testing the foodware item themselves.
Personally, I would never use any foodware item from China without first leach testing the item. This can be done by purchasing a leaching test kit.
As for glass items, the same holds true as lead is commonly used as a fluxing agent in glassware to create a more brilliant reflection. If not heated to the maximum maturing temperature, lead can leach from these products too. The only way to know if the item is safe is to leach test it.
I know this sounds complicated when a consumer needs to determine whether their foodware contains such toxic ingredients in the makeup, but responsibility falls on the consumer to ultimately determine if their ware is safe to use.
In conclusion, you should also beware of ceramic items made in the United States through private studios. Inexperienced potters, those who have not studied glaze chemistry, may not understand or fail to follow common sense when formulating glazes in their studios. I have experience in studios that still use raw lead in their glazes. This is unacceptable, in my opinion and should fall under the same or greater regulations for safety.
I teach clay and glaze chemistry and in my teaching materials, fully cover the safety issues involving lead and other toxic materials used in glazes. However, very few educational studios, as well as universities with basic ceramic programs teach this type of glaze education. Therefore, once again, the burden of discovery lies with the consumer.
If you want to be sure a piece of ceramic ware is safe, have it tested or test it yourself. You can purchase a testing kit by searching online for leach test. Otherwise, I would consider the piece unsafe until tested and not used for any reason when in contact with food. This may seem extreme, but if safety is an issue to you, then this extreme caution far outweighs the results that may occur should you consume food items with leached toxic materials.
As for your question about ceramic and bone china, they are just clay identification and should be considered as part of all ware manufactured from China. It is the glaze that is the concern, not the clay body. I can tell you that usually glazes fired on China clay is fired far beyond the melting point of lead and renders the glaze leadless as the lead vaporizes at those temperatures. Therefore, high fire glazes should not contain lead. But identifying foodware as being high or low fired is impossible for the consumer and sometimes manufacturers use a lower maturing glaze on a high fire clay body to save costs in firing. The only way a consumer would be able to identify this would be to break the item and examine the clay and glaze fusion under a magnifying glass. If the clay and glaze didn't fuse together then the glaze would be suspected as being low fire and could contain toxic materials. Fusion occurs when the glaze a clay raw materials fuse together, resulting in a third section between the clay and glaze body where the fusion took place. The larger the fusion section, the better the strength of the ware and the less likely the ware will have leaking issues due to the porosity of the clay body.
I hope this answers your questions. If you have further questions, please feel free to contact me at any time. I am always at your service.
Ms. Ti Phillips
Earth Stoke 'N Fire Pottery Studio and Artist Retreat
---------- FOLLOW-UP ----------
QUESTION: Dear Ti,
Thank you for your detailed reply.
Q: So the FDA regulations that might halt the importation of contaminated tableware took effect in December 2012?
I had previously been on the FDA website and was surprised to read a list of countries whose tableware shipments had been detained because of lead and cadmium. I am Canadian. Canada was on that list and France, England, Germany, Italy…..and of course Chinese and Mexican shipments were there in droves.
I had always thought tableware from Canada, the US and England was safe. I decided when I read that list, that I should get a lead testing kit, but what about cadmium or other toxic things of which I am not aware?
Q: Is the leaching test kit for lead only?
Q: And once an item has been tested with the kit, is the item in some way contaminated by the testing chemicals?
I looked at the list on the FDA site of safe manufacturers in China. I doubt even the retailer would know which manufacturer made the products they have in their store. Many mugs have only "China" stamped on the bottom.
Q: Is bone china able to be tested with the leaching test kit? The breaking and examining is not necessary if I were to use the test kit?
Q: If present, would the lead always show up in new tableware using a leaching test or might some items test negative when new, but positive once they were more worn?
Thank you again.
Thank you for your recent follow up questions. Yes, the regulations took effect in December 2012, however, it was the early 90's when the FDA brought the matter to attention and begin compiling the lists for safe manufacturers.
There are various leach testing kits available depending on which metal you are wanting to test. Barium, lead and cadmium are three of the kits. Mercury is another, but this metal is not used in ceramics.
The each test has instructions on how to perform the test. And no, it will not harm your food ware.
You do not have to break a pottery piece to check it for toxic metals. All ceramic ware is able to be checked with the kits.
If any of the toxic metals are present, the test kits will identify them whether the ware is new or old.
I know that there are many tests to check pottery for safety. This can become expensive. So to begin with, use the following instructions to test a pottery piece before purchasing a kit. This will give you an idea if there is any toxic metals that could leach from the ware. It will not identify the metals, but will let you know if the glaze on the ware leaches.
Home Test for Leaching Ware
Slice a fresh lemon into 1/4" slice.
Slice the lemon round in half, exposing the citric side.
Place the cut lemon on the glaze in question.
Leave for 3 days without moving.
If testing the inside of a cup, lay the cup on its side.
On the fourth day, remove the lemon.
Wash the item in soapy water.
Examine the glaze.
If there is a lemon shape on the glaze, or any discoloration, the ware can leach.
Further test the ware with a test kit.
Do not use the ware until it is determined that it does not have leaching toxic materials.
I hope this answers your questions. If you have further questions, please feel free to contact me again any time. Always at your service.
Ms. Ti Phillips
Earth Stoke 'N Fire Pottery Studio and Artist Retreat