Green clay yixing toxic?

[britt]

Hojo states that green clay eliminates taste. I'm assuming you are refuting his statement when you say you are getting better tasting Wuyi from it. So, you can still taste the tea using green clay. Maybe Hojo's statements are not translated properly.

I've never heard of any tea people recommending green clay over red and purple clays but the green clays are naturally occurring in yixing. If they are using green clay without additives, firing the pots high enough where porosity is not an issue, I don't think they are toxic. But, I can't speak for people who may have hyper-sensitive conditions.

No teapot should smell when brewing tea or just plain hot water in it. Good yixing has the same aroma as heated stone. I would never use or even attempt to season a teapot that smelled. Something is wrong.

I'm not familiar with Hojo's comments on Yixing green clay but if he does say that, then I do dispute it. That doesn't mean I don't believe he experienced some detrimental characteristic with green clay, only that I haven't with this particular Yixing. The Jing Tea Shop product description was as follows:

"A rare piece made using a special recipe clay from the Yixing teapot factory I. It was originally designed by famous artist Mr. Shi Xiao Ma, who is one of the most well known artists of Fang Qi (squarish items) making. The whole teapot has a smooth and tender texture combined with spirit and well designed lines. The exciting point is the delicate detail from the lid that can clearly show the complicate work of this teapot. The whole piece announces a calm and ancient feeling that is inspired from the ancient Chinese jade arts. This teapot is a true keeper. By experience, as we are using a same clay teapot, this special receiped Lu Ni works well with traditional heavily roasted Wu Yi oolong tea."

I know when I purchased this from Jing Tea Shop I was lucky enough to see it just as it was being posted, so I grabbed it. Sebastien later told me I only beat others who tried to purchase it by a few seconds. Quite some time after that, he said customers were still asking about this pot and whether he could get more of them. As far as I know, he never did.

A co-worker who returned to China on vacation came back with what he thought was an exceptional purchase. Besides a duan ni Yixing, he also had a green clay Yixing complete with cups and saucers made from the same clay. He thought this was a prized possesion and was quite pleased with himself for having found it. He claimed, whether right or wrong, that this is the best clay for a teapot, and the most expensive.

I also would refuse to bother with any pot that had a bad smell. I doubt that problem was because of the green clay, but was probably due to some other reason. I never noticed any smell from Jing Teashops Yixings, but I still boil them for at least a half an hour before I use them to brew tea in.

[tingjunkie]

The blue/green clay is called Muo Lu Ni. I have one of these and I have to say it is my favorite teapot out of all the ones I own. I use it for traditional kung fu preparation of high fire TGY, and it's a killer. The original clay from Ben Shan Mountain is pretty much extinct, and is faked quite often.

Britt, if your pot is indeed Ben Shan Muo Lu Ni, then treasure it. It's a collectors piece for sure. Any chance you could take a photo with accurate colors? I'd be interested in comparing the color of the clay to the one I have.

[Tead Off]

Hojo states that green clay eliminates taste.

What does Hojo say about Yellow Division Clay - I have a collection of these that I use for Anxi oolongs ?

Are you referring to Duan ni clays? They can be very pretty like the lu ni clay. I've never used either yellow or green teapots so I can't speak from personal experience. In my discussions with Hojo, he is dismissive of yellow, green, and, brown clays. He categorically states the superiority of red (zhu ni) and purple (zisha) clays. Is he right? IMO, nothing beats zhuni but, I use other red and purple clays and get good results.
Hojo introduced me to the idea of taste testing different materials with the same tea. I've posted this before. It works. Very quickly you can experience the difference between one pot and another and its effect on the same tea. There is an X factor, though. The Drinker.

[Herb_Master]

There is an X factor, though. The Drinker.

I visited Hojo and Hui gave us the water taste comparison of Glass, Banko and Shigaraki - I am sad to relate that both I and my partner were hard pushed to detect any difference even with all the help Hui was giving us by telling us the differences we were supposed to detect

[isaac]

I thought I will update my status. I met a fellow collector coincidentally twice. He gave me some pointers and as a result, today the smell is gone.

I will continue to season the pot for the next two months before using it. It has developed a very nice glow, not shiny but more of a lustre.

Well, thank you everyone and i am glad that it generated so much discussion. Especially thanks to John for his useful information.

I wish i can contribute knowledgeably to the discussion but that will be expecting too much of a person who came to love zisha pots two weeks ago.

One of the reasons told to me why green clay is not as popular is because of its propensity to stain. I experienced this first hand as my teapot became speckled with black dots. I used a toothbrush and brushed the pot with toothpaste rinsing and scrubbing again for over two hours before 80% of the black dots disappeared to be replaced by the gold sand. However there are other opinions to counter this - that you can use green clay to brew a cup of puerh.

Anyway do continue your discussions. They are enjoyable to read.

[Tead Off]

There is an X factor, though. The Drinker.

I visited Hojo and Hui gave us the water taste comparison of Glass, Banko and Shigaraki - I am sad to relate that both I and my partner were hard pushed to detect any difference even with all the help Hui was giving us by telling us the differences we were supposed to detect

Ahh, the X factor! In my case, I wasn't led into anything. Nothing was mentioned about what I was supposed to taste or smell. My wife was at my side tasting the same teas I was. We could hardly agree on anything except how sexy those tetsubin were. When it came to the comparison of the yixing vs Sado, I was shocked how much better the yixing was. What was most surprising was the difference in using Banko with a young Puerh. The X factor is all that matters.

[Herb_Master]

Hui only mentioned after we had tried the water from all 3 and asked us to try again.

[JBaymore]

I experienced this first hand as my teapot became speckled with black dots. I used a toothbrush and brushed the pot with toothpaste rinsing and scrubbing again for over two hours before 80% of the black dots disappeared to be replaced by the gold sand.

Interesting. Were the "black dots" on the inside or the outside or both? Was there a "grain of sand" directly under the black dot that came off? How big were these dots? Did the dots stain the cleaning medium in any way? What kind of tea had you brewed before the dots showed up?

best,

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

[isaac]

Interesting. Were the "black dots" on the inside or the outside or both? Was there a "grain of sand" directly under the black dot that came off? How big were these dots? Did the dots stain the cleaning medium in any way? What kind of tea had you brewed before the dots showed up?

They were on the outside. I did not observe the inside. Possibly they were tea stains that sit on top of the sand embedded in the teapot. For some, a light and gentle scrubbing is sufficient to remove them. For others, need more persistence. Naturally i used a soft brush and minimally abrasive toothpaste

John, there is an easy way to differentiate the smell of a green clay teapot from that of others. Apparently it will also work with teapots of a black colour (not dark brown or dark grey to the point of black but those which are truly black). Put two teapots side by side, one green and the other purple (best if purple), both zisha. Fill both with boiling hot water. Cover the teapots. Smell the rim of each teapot. The two rims should have dissimilar smells. I tested this on several pots and it works for those pots. Leave overnight. The next day, smell the inside of both teapots. Again the smells will be dissimilar.

Note: Please take all precautions with the boiling water; both pots must be new, unseasoned and made of pure zisha. The potter is not important for this experiment. Do not pour the hot water immediately into the pot but over the rim first, then the exterior and finally the inside of the pot.

[britt]

Britt, if your pot is indeed Ben Shan Muo Lu Ni, then treasure it. It's a collectors piece for sure. Any chance you could take a photo with accurate colors? I'd be interested in comparing the color of the clay to the one I have.

I'm sorry but I don't own a camera or a cel phone, so I have no way to take an accurate picture. I'm usually far behind the curve as far as technology goes.

I just took another look at my Lu Ni and I must say I don't really see any blue in it. It is a rather deep green that has picked up a nice shine very quickly. It is dedicated to Wuyi, which I don't drink that often, yet with this limited use the tea oils seem to absorb into the clay pretty fast. It is much shinier than when I bought it.

[chrl42]

It might be toxic.

On the other hand, there are clays used by Factory-1, they were Germany-imported cobalt oxide and chrome oxide which were already more expensive than tons of clay..these powders were allowed to be used 0.5% of total amount of clay

Temperature also affects it, high-fired clay won't likely emit out the hazardous effect (though still does)

But that's to rule out Factory-1 clays and they are still to harm bodies even if it's little (iron oxide and manganese oxide aren't)

but that's my story.. collectors don't believe they might be harmful to bodies, the one used is cobalt 59 which is just as same as iron in effect

But normal green clays on the market..ewww

[JBaymore]

Just to again be clear here......... high firing (which can itself be a somewhat nebulous term) is absolutely no guarantee of the stability of the ceramic chemistry of either clay bodies nor glazes. What is the determining factor in any potential leaching is the combination of the clay bodies formulation (or the glazes formulation), the exact firing profile (as in rates of climb, atmosphere at certain points, etc.), and the end cone achieved (not necessarily the temperature but the "heat work").

High firing makes it easier to create stable compositions.... but it is no guarantee. High firing can lessen the leaching issue in "poorly formulated" stuff..... but it does not automatically stop it. High firing decreases the likelihood of leaching from what might be looked at as "non-technically considered" clay and glaze formulations, but it does not assure that.

Fast example:

I can take a number of certain "high fire" (end point Orton cone 10) green American Oribe-style glaze that you can lay a fresh cut lemon slice upon for 12 to 24 hours....... and you'll get the impression of the lemon nicely visibly etched into the glaze surface. That glaze leaches copper to beat the band. It is high fire. To casually look at it, it looks like most other Oribe-style glazes you have seen. You can predict the leaching using ceramic chemistry software, and you can do the standard leaching tests to confirm it. But the "lemon slice test" easily points the way.

Relative to the possible additions to the clay bodies mentioned above, in a sort of heiarchy of any "potential concerns" sequence, maybe also have a look here........

Manganese Dioxide
http://www.jtbaker.com/msds/englishhtml/m0715.htm

Cobalt Oxide
http://www.jtbaker.com/msds/englishhtml/c4961.htm

Chrome Oxide
http://www.jtbaker.com/msds/englishhtml/c4356.htm

Iron Oxide
http://www.jtbaker.com/msds/englishhtml/f1306.htm

Remember that the nature of the leachate can vary greatly. Just because something is present in a clay body or glaze does NOT mean that it WILL leach. Just that it is there to potentially leach. If a clay body or glaze is unstable, and it only contains compounds that are relatively non-toxic (alumina, silica, sodium, potassuim, calcium, magnesium, iron, etc.) ... then it does not matter too much that it is leaching. It is when there are potentially toxic compounds present that the issue becomes of concern.

best,

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

PS: New readers... PLEASE read the whole thread to get context.

[chrl42]

JBaymore, that's hella helpful information, hehe. Thanks a bunch.

I might take the info you provided to Wang Jun Hua (Chairman of Zisha association)..though I doubt he'd take so seriously, since having undertood the Chinese

Last time this topic was brought up, the experienced Chinese collector brought red wok, blue wok, basically implying 'then everything else in modern world is toxic'

BTW, Factory-1 was goverment-owned factory, they did take a test regarding toxic issue with those iron, coblat-oxide-clays, and the answer was 'yes it is harm, but just as harm as drinking water', plus they demonstrated the fact those oxide powders were imported goods, implying the safety issues.

Anyways, this toxic issue keeps runinng and discussed, and still needs to be discussed..and we need more men like you!

[bagua7]

...It is when there are potentially toxic compounds present that the issue becomes of concern...

As customers how should we know when teaware contains any of the aforementioned toxic compounds? Honestly, we can't unless you have the privilege of having access to a toxicology lab with a PhD assisting in the risk assessment of that particular teaware.

Basically we are adrenaline junkies for using Chinese teaware, aren't we?

What to do then? Stop drinking tea?

[isaac]

I spoke with a tenren salesman and he told me that his pots are from Taiwan; some of them are made from yixing clay imported from China. Presumably they did their quality checks on the clay before buying them.

For what it is worth, they are selling in the United States too. You might like to visit their web www.tenren.com and browse through their teapots and store locations.


As for the actual chinese yixing teapots, whilst price is not a definitive indicator that a teapot was not made from clay with additives, it is a general indicator that it might be made from genuine clay. Zisha is an expensive raw material and it is unlikely the potter will pay $1 for the raw materials and sell the finished product for $2.