Feb 12th, '15, 17:00
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Re: Results of lead/cadmium leach test of Yixing with S.G.S.

by xiaobai » Feb 12th, '15, 17:00

JBaymore wrote: I spend a lot of time in Japan... and here is another 'interesting' factor that people likely are not aware of outside of people who are 'in the field'. After the meltdown at Fukushima, the wind deposition patterns dropped a lot of radioactive materials into the area of Mashiko... one of the major pottery centers. The potters there were advised that they could not use fire wood for their kilns from that area until further notice (still banned) because the fly ash was concentrating the radioactive residue into the shizenyu (natural ash glaze) on the works. In the typical culture of Japan .... hopefully most potters are complying.

I will be very interested to see whatever more work you do on this study.

best,

...................john
Interestingly, my wife and I visited Mashiko one year before the accident, while I was a visiting scholar at the Institute for Solid State Physics, in Kashiwa-no-ha, Chiba prefecture. We still keep in our cupboard the yu-samashi that we made and had fired there.

I wonder if the accident in Fukushima has also affected other pottery centers in Tohoku. Recently, we went to Sendai and bought a couple of pieces of Tsutsumi-yaki (I use them to kid my wife, because the name, when written in Kanji, looks very similar to her family name. :wink:) I was surprised to learn that that the number of Potters in this tradition has dramatically decreased in recent years... :(

I am off to Ali Mountain and Sun-Moon lake for a couple of days. Will be drinking hongcha and Oolong along the way. I will post the final report for the Chen Ju Fang's pot from Essence of Tea upon my return.

Have a good week end!

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Feb 12th, '15, 20:50
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Re: Results of lead/cadmium leach test of Yixing with S.G.S.

by kyarazen » Feb 12th, '15, 20:50

JBaymore wrote: Next we have to look at the duration of the exposure. For us, the duration is the time we spend drinking the tea and the time it is in our bodies digestive system before being excreted. You body has an amazing ability to deal with many "insults". The shorter the duration of the exposures..... the more time you give your body to do its job and to deal with the problem and recover from it. Iff you drink constantly all day from that same cup mentioned above, that is a different duration than if you have one cup a day.

For another example, copper is generally not thought to be very toxic if it leaches from a glaze. It affects the taste of foods... but would have to be in really high levels to be worrisome. BUT... if you are the person with the rare Wilson's Disease........ a small amount can kill you.
its interesting but in the recent years, major drug companies that i had been acquainted with in research had defined "health" as the ability to deal with insults, and that of good health is to have a higher threshold vice versa..

copper is not an issue on the whole, but heavier metals tend to have visible effects on neurotoxicity especially when neurons dont really divide much nor regenerate (much).

Feb 13th, '15, 23:59
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Re: Results of Yixing lead/cadmium leach test with SGS

by ryancha » Feb 13th, '15, 23:59

Thanks for all the information, John. Its very helpful--and I never suspected all these issues.

It almost seems that dealing with clay, glazed or unglazed, isn't worth it! In China, we have an industrial miasma; in Japan, radioactivity; and everywhere, incorrect firings, etc...

Of course, as xiaobai points out, I'm sure there is plenty I don't want to learn about the leaves themselves!

Feb 14th, '15, 08:14
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Re: Results of Yixing lead/cadmium leach test with SGS

by ethan » Feb 14th, '15, 08:14

kyarazen, I have not found r.o. water to be quite nice for tea. It is not as bad as distilled water but has much of the negative results. I do not know milliQ which may be a special type of r.o. water.
Water devoid of minerals seems to have a problem giving the tea something to hang onto, lessening flavor and body.
Perhaps the experience of other teachatter is the same as mine.

Feb 16th, '15, 03:04
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Re: Results of Yixing lead/cadmium leach test with SGS

by xiaobai » Feb 16th, '15, 03:04

This is last report for this batch of teapots.

The pot is a modern shi piao and was made by Chen Ju Fang using
aged Huanglongshan clay. It sold by The Essence of Tea (EoT).

More pictures for this pot are available from the EoT website:

https://www.essenceoftea.com/teaware/cl ... eapot.html

Although it is a pain to clean the pots after the test,
I plan to submit more batches for test with SGS in the future.
My next batch will consist mostly red clay pots.
I will continue posting the results on this thread.

I would also like to encourage other TC readers who have tested their pots
(at SGS, using test kits, or anything else) to report the results here. Hopefully, together we can build a resource on TC that will inform other people about reliable vendors and places to obtain safe to use Yixing ware.

Peace!
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Feb 16th, '15, 22:06
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Re: Results of Yixing lead/cadmium leach test with SGS

by Tead Off » Feb 16th, '15, 22:06

How much does this test cost?

Feb 16th, '15, 23:16
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Re: Results of Yixing lead/cadmium leach test with SGS

by xiaobai » Feb 16th, '15, 23:16

The quotation that I was given by SGS was (US$) 40 bucks (without tax),
which translates (at the current exchange rate) into NT$1200 (NT$1260 incl. tax) for one pot.

I think this is relatively little compared to the price of a good Yixing
teapot.

Frankly, I do not understand why more vendors do not perform the test.
My impression (from exchanges with some of them) is that they ignore
it is relatively inexpensive (unless you are selling 30-buck pots...)

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Feb 17th, '15, 06:43
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Re: Results of Yixing lead/cadmium leach test with SGS

by Tead Off » Feb 17th, '15, 06:43

xiaobai wrote:The quotation that I was given by SGS was (US$) 40 bucks (without tax),
which translates (at the current exchange rate) into NT$1200 (NT$1260 incl. tax) for one pot.

I think this is relatively little compared to the price of a good Yixing
teapot.

Frankly, I do not understand why more vendors do not perform the test.
My impression (from exchanges with some of them) is that they ignore
it is relatively inexpensive (unless you are selling 30-buck pots...)
Have you been in contact with any Yixing users that have had good pots tested with positive results for contaminants?

Feb 17th, '15, 07:33
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Re: Results of Yixing lead/cadmium leach test with SGS

by xiaobai » Feb 17th, '15, 07:33

Tead Off wrote: Have you been in contact with any Yixing users that have had good pots tested with positive results for contaminants?
No.

So far, I only know through TC that Kyarazen tested his selected teaware and the pots tested negative.

Do you know someone whose (good or bad) pots have tested positive?

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Re: Results of Yixing lead/cadmium leach test with SGS

by JBaymore » Feb 17th, '15, 11:03

Tead Off wrote: Have you been in contact with any Yixing users that have had good pots tested with positive results for contaminants?
THAT would be an interesting piece of information to establish. At the moment the concerns are apparently "heresay" and "supposition". Knowing it IS actually happening would help clarify the potential issue.

We clearly have some "exclusion" data right here in the work done xiaobai (incurring personal out-of-pocket expenses).

BTW....... leach testing is about the same price or just slightly higher here in the USA.

best,

................john

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Feb 17th, '15, 11:21
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Re: Results of Yixing lead/cadmium leach test with SGS

by Tead Off » Feb 17th, '15, 11:21

I don't know anyone who has had their Yixing pots tested. I've also never heard any 'hearsay' about Yixing clay being contaminated, but wouldn't be surprised if there was, as China has about as bad a reputation for pollutants and contaminants as any country could have. Leaking would definitely be the prime vehicle for contamination of the mines. But, I would think that the gov't and business community surrounding the pottery industry in China would have done some testing by now, as Yixing is no small matter to the Chinese as well as some of the richest people in the world.

Feb 17th, '15, 21:15
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Re: Results of Yixing lead/cadmium leach test with SGS

by xiaobai » Feb 17th, '15, 21:15

Tead Off wrote:I don't know anyone who has had their Yixing pots tested. I've also never heard any 'hearsay' about Yixing clay being contaminated, but wouldn't be surprised if there was, as China has about as bad a reputation for pollutants and contaminants as any country could have. Leaking would definitely be the prime vehicle for contamination of the mines. But, I would think that the gov't and business community surrounding the pottery industry in China would have done some testing by now, as Yixing is no small matter to the Chinese as well as some of the richest people in the world.
I think we are jumping to the conclusions too fast. One of the reasons why I decided to go ahead and test my pots is because I am tired of reading exchanges on TC discussing whether Yixing pots are contaminated or not.

I would like to emphasize that my study was done on a rather small sample (5 teapots, obtained from relatively reliable vendors). I did not test any red clayware, of which there are concerns it may be mixed with (possibly) contaminated oxides. In fact, that is my next task, as soon as I save up some money for it. So, we cannot extract many conclusions about the Yixing industry from this study.

In addition, as I already pointed above (and so did John) there are environmental reasons to believe that Yixing and Jiangsu are extremely polluted places. If somebody is still skeptical and is holding strongly to the rather romantic image of Yixing, he or she should take a look at this map of the so-called "Cancer villages" in China:

https://www.google.com/maps/d/viewer?ms ... GsxnMyxV3c

and notice the astonishing concentration of them located in Jiangsu province, not far from Yixing.

Let me also point out that I am not the first to test Yixing pots in Taiwan. One of my most trusted vendors, Mr. Su from Taichung, has been doing it for a while. In fact, I am following the idea of sending my pots to SGS taking his practice as example. Please, see:

http://www.puwangtea.com/%E6%82%A8%E6%9 ... 80%BB.html

Use Google translation if you cannot read Mandarin, to get a rough idea of what is going on. Mr. Su is not only a tea vendor, but also teaches about Tea Culture and Yixing Pottery at National Chung Hsing University in Taichung. He has been to China many times, has bought ores there himself, and has commissioned the making of teapots that he sells in his shop. The pots are expensive and a bit on the large size for my taste, although I own a few of them. He always tests four samples for each type of ore (modern zhuni, duanni, zisha) out of the contamination concerns. But of course, he would not sell or tell you about anything that has tested positive (probably not, because he controls the entire process, something that we, as customers, cannot afford).

At the bottom of the same web page, you will find the links to the videos of the documentaries made by CCTV, which uncovered the scandal.

Therefore, that there is contaminated Yixing clay around, I think it is undeniable (wert also pointed to me in private communication that
some lead tainted had been used in the making of slow cookers in 2008 by
a famous brand. Maybe he can provide more details about that scandal).

Whether the problematic clay has made it into the "good teapots" that Tead Off was referring to above, I have no idea. But, to quote Donald Rumsfeld:
" There are known unknowns [...] But there are also unknown unknowns. There are things we don't know we don't know" about the Yixing Industry
in China.

Therefore, instead of continuing discussing 'unknowns', let's take a pragmatic (experimental) approach and test and measure. And discuss with real data on the table, instead of just assumptions.
Last edited by xiaobai on Feb 17th, '15, 21:32, edited 1 time in total.

Feb 17th, '15, 21:25
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Re: Results of Yixing lead/cadmium leach test with SGS

by wert » Feb 17th, '15, 21:25


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Re: Results of Yixing lead/cadmium leach test with SGS

by kyarazen » Feb 17th, '15, 22:17

white paint in the states before early 1950s contained up to 50% lead..
similarly yixing before 1958 they were extremely comfortable with using white glazes containing good amounts of lead (refer to the ROC and earlier 开片白釉). the chinese no doubt did love leaded colors. imperial palaces used decors made of 琉璃 glass, using various transition states of lead to give the lovely colors. if melamine was used to dope baby milk powder on large scale, what is lead or heavy metals into a non edible crunchy pottery?

A caveat though, i had seen reports in the chinese forums that some pots were tested to leach 0.04-0.06mg/L lead, almost at, or below the minimum acceptable detection limit of ICP-AES (0.1ppm). although I used GF-AES, which gives an mdl of 5-10ppb for lead, perhaps the most obsessive compulsive should consider picking a grain of clay from a discrete area i.e. inside the spout or internal filter area for ICP-MS...

in one's blood, if 0.1ppm of lead is detected, it may be worthwhile to seek clinical attention.

lead in the environment is unavoidable, it is in the soil, it is in inks, it is in ceramics, it is in water. the limit now is on what level should it be considered unacceptable by health standards. heavy metals, large amounts of lead, wee amounts of mercury, etc wont really kill a resilient human being. the only concern is the quality of life, since these substances are mostly neurotoxic (and neurons dont regenerate much) and they are cumulative.

less concerned about manganese though, even tea leaves or brewed tea can contain more manganese than whatever that can leach from pots.. :)

Feb 17th, '15, 22:50
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Re: Results of Yixing lead/cadmium leach test with SGS

by steanze » Feb 17th, '15, 22:50

Good point, it can be useful to start from the question of how much of these minerals there is in tea.
http://www.researchgate.net/publication ... tamination
http://www.ncbi.nlm.nih.gov/pubmed/16118651
http://www.tandfonline.com/doi/abs/10.1 ... OQJ_81Gh5Q

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