Lead in Ceramic and Porcelain Cup (Gaiwan) - Safe or Danger?

by Boris
(Crotia)

Julian, I asked my tea shop about lead in ceramic or porcelain ware (such as a gaiwan I bought from China) and they say:

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Thank you for visiting our tea shop and for your inquiry.

In traditional Chinese porcelain making, lead can be used in the painting when the artist is using gold or silver. It will be used with a mix of gold to facilitate the melting of gold or silver.

This is mostly used for decorative piece and if there were to be any on tea ware, it would be on the outside and not the inside.

We do not have currently any porcelain tea ware that contain leads and if we did, we would put a disclaimer.
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Can I trust my vendor? What's your recommendation?

Answer:

Boris, I have not had experience dealing with ceramic ware directly so I am not an expert. What I am aware of is this issue has been a concern to FDA and the Chinese authority.

And where there is smoke, there is fire. We would rather be safe than sorry.

The main risk, of course, pertains to children. The main risks to tea drinkers are that we use hot water, and can drink up to many cups a day.

A cursory search through the web reveals the following extracts from various sources.

Australian Government:

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.

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.

Source: http://www.environment.gov.au/atmosphere/airquality/publications/ceramics.html

My reading from the above is that the risk is present, and greater for developing countries, smaller manufacturers where control is lacking. Handmade porcelain, antiques are also at risk.

Universiti Sains Malaysia 1995 Study

Ceramic tableware has long since been recognised as a source of lead poisoning. Locally available ceramic utensils (cups, bowls, sauce plates, cooking pots and spoons) were examined as possible sources of lead poisoning. The lead was leached out with 4% acetic acid stored in the samples at room temperature for 24 h.

Overall, 54.7% of the sample items tested exceeded the US PDA maximum permitted lead release from earthenware. Of the sauce plates 83.7% exceeded the safety limit and released the highest levels of lead. The amount of lead leached out from the samples decreased with repetitive teachings and increased with temperature. Lead is also found to be leached into acidic foods such as thin soya sauce, tomato sauce and tamarind juice stored in samples of ceramic sauce plates for 24 h at room temperature.



Source: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T6R-3YYT6DF-J&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=957215135&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=fb7e198216ed237a4e848eba2a0c6dab

So, what can I say? The risks are indeed prevalent in Malaysia, and possibly in other countries.

Frogpondpottery.com

Written by a potter, the author argued that lead frit is safe for the artists, but equally dangerous for consumers.

If the artists use a food safe glaze, it doesn't make it much safer because his kiln may have different temperature compared to the glaze manufacturer.

Myth: Using lead in fritted form makes it safe

Fact: Lead-containing frits are indeed safer for the potter to handle than the various forms of raw lead. The use of frits, however, has ABSOLUTELY NOTHING to do with the safety of the final glaze. Once the glaze is melted in the kiln, the lead no longer knows it was contained in a frit. The only things of importance from this point on are the composition of the glaze and the firing conditions.

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Myth: If I use a commercial lead-containing glaze which indicates that it is food safe, it is.

Fact: This is only true if your firing conditions and things like underglazes are exactly the same as those used by the glaze manufacturer. In fact, most kilns have significant variation in temperature and your firing conditions, at least in part of your kiln, are probably significantly different from those used by the glaze manufacturer. A copper-containing underglaze may significantly affect lead release. The only way to assure that a lead-containing glaze is safe for use with foods is to have representative pots from every firing tested by a qualified laboratory. In addition FDA regulation in the United States requires that potters have a qualified laboratory periodically check their ware. Ware that might be used for food, but does not pass the leaching standards must have a hole drilled in the bottom or be permanently labeled that it is not safe for food use. California requirements are even more specific and stringent.

Source: http://www.frogpondpottery.com/pottalk/lead.htm

FDA

Michael Kashtock, Ph.D., chief of FDA's Office of Plant and Dairy Foods and Beverages enforcement branch, says,

"FDA allows use of lead glazes because they're the most durable. But we regulate them tightly to ensure their safety. Commercial manufacturers ... employ extremely strict and effective manufacturing controls that keep the lead from leaching during use."

Small potters often can't control the firing of lead glazes as well, he warns, so their ceramics are more likely to leach illegal lead levels, although many do use lead-free glazes.

"The best advice is to stick to commercially made products. If you are going to buy something hand-made or hand-painted, get assurance that lead-free glazes were used," he says.

Antique ceramicware may leach high levels of lead.

Consumers can use a lead test kit from a hardware store on such pieces and on other hand-painted ceramicware they may already own.

Avoid using such items--particularly cups, mugs or pitchers--if the glaze develops a chalky gray residue after washing.

Source: http://vm.cfsan.fda.gov/~dms/fdalead.html

How to be Safe

- For steeping green tea, I would use a glass ware rather than ceramics. Glass helps to disperse heat and that suits my style as I like using very hot water.

- Where I need to use a porcelain ware, such as when brewing oolong, I would get my brewing vessel from a major manufacturer rather than from some handmade artisans from third world countries.

- Lead free product is the way to go. Made in a developed country would give some comfort.

- Get a lead testing kit? Worth thinking about, especially the bath tub, other cups and mugs, or anything my children use would be at risk. But no guarantee that it will work if it says everything is okay.

I hope this helps.

Julian

Comments for Lead in Ceramic and Porcelain Cup (Gaiwan) - Safe or Danger?

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Jul 14, 2009
Borosilicte glass
by: Boris

Detailed answer! And what about borosilicate glass that is also becoming popular lately? Is it safe?

Jul 25, 2009
Korean celadon
by: Boris

A vendor of korean celadon products told me they don't use lead:

"Korean celadon uses no lead in its production. The clays are local Korean clays and the glaze uses iron to achieve the beautiful green, celadon color."

I don't know if this is valid. Any suggestions?

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