joelbct wrote:There has been some talk of lead/ other dangerous elements/compounds in teaware lately. Does anyone have any links to scientific documents about this?
Also, someone said to stay away from metallic glazes. Does this include bizen-ware? Does anyone have info on particular glazes that are bad, or is this just a case by case basis? Would be nice to know whether a teaware glaze would leak lead *before* we shell out the $, rather than buying it first and then testing it...
Likewise, a list of glazes/ firing styles that are typically safe for drinking tea would be nice too...
Bizen is unglazed by definition, so metallic glazes should not be a problem with bizenyaki or other unglazed pottery (such as Shigaraki).
The raku question is a bit complicated. Note that American raku - the kind that usually has a metallic glaze with an iridescent sheen - has a very different composition from traditional Japanese raku (black and red). Both types of raku are made with lead, but in the case of Japanese raku, it is safe to drink from raku chawans under particular circumstances. My understanding is that American raku is generally unsafe to use for eating or drinking - that is why so many American pieces are labelled with some sort of "For ornamentation only; do not use for food" label.
On Japanese raku, the Tea Toys facts page
Real Raku, made by the family of Raku Kichizaemon and his 14 generations of ancestors in Kyoto and the 11 generations of Ouhi Chozaemon's family of Kanazawa is very different from the low temperature, pit-fired and dipped in all kinds of oily stuff that is called "raku" in the West.
Since the 16th century, amateur tea masters and craftsmen have made another, similar type of ceramic into teabowls, ash bowls, flower vases, incense burners, mukozuke dishes for kaiseki, etc. These ceramics are called rakuyaki in this catalog. The techniques for making them are hardly different from those used by the two "Real Raku" making families; the difference, as far as I know is the clay (not always being 3 generations old), the exact glaze formula secrets, and the generations of skill in firing.
The rakuware handled here is made with a tiny proportion of lead to make the glaze melt at the low temperatures rakuware is fired at (approx. 1000 C for black; 800 C for red; "real Raku" is fired at 1200 C and 1000C respectively). [...]
The only danger from lead in any glaze comes with prolonged holding of an acid liquid in the utensil, which will leach out the lead. This should NEVER happen in a rakuyaki teabowl, since the matcha is not acid in nature and it is in the bowl for such a short time.
One way to help keep the bowl clean in the pores is to soak the bowl for about 5 minutes before using. I heard this directly from the present Kichizaemon 15th himself. Especially in winter, if you use hot water, the bowl will not absorb the heat from the tea and even the last guest will get a drink of hot tea; too hot and the poor shokyaku [guest] can hardly drink it much less savor the flavor, so finding just the right temperature requires much experimentation. Soaking too long is a bad idea, I can say from personal experience, because the "special smell" of the clay becomes too strong. [...]
Needless to say, you SHOULD NOT use vinegar or citrus juice of any kind [in raku wares].
So, here's yet another reason for preheating the bowl with hot water prior to whisking the matcha in it
Frankly, I have never heard anyone express reservations about safety or lead levels in Japanese wares, other than the perennial question about raku. My own concerns have to do with Yixing (or Yixing-like) pottery. How do you know when a Yixing pot is safe? How can you be sure that a seller's wares are OK to drink from? The seller may be reputable, but what about his suppliers...?