Oregonian Haruspex > wrote:
>The "real" red yixing ran out in the 1970s or so. There are several
>substitutes on the market varying in color from red (not the same lode
>of clay as the original) to purple to brown. In the past it seems that
>yixing clay of varying shades was used as well.
I did not realize that this was the case. This would explain a lot about
the current state of the market, indeed.
>Since manufacturers of these products do not seem interested in details
>about the production of their wares, it's tough to say for certain that
>we know much of anything about them. The high aluminum content in your
>sample is suspicious to me though - seems way too high. The Chinese
>are sneaky and have been known to put all kinds of fillers into things
>if they can get away with it.
>
>If you can acquire a few samples of the older ware, preferably
>pre-industrial, and have the mass spectro guys run those too I think it
>would be most helpful.
If I actually had such samples, I would run them, but barring that I
spoke to Jon Singer who knows both tea and pottery, and I include here
part of his reply by permission:
Jon Singer writes:
>
> Let's compare with with an analysis done for me a bunch of years ago by
>Mary Simmons, who (IIRC) was at the Univ of New Mexico at the time:
>
>
> Yixing
>
> Yixing P Yixing G Yixing R Red Clay
> SiO2 60.15 71.67 56.56 58.911
> Al2O3 20.50 19.03 20.43 16.995
> K2O 2.11 1.69 2.04 3.426
> Na2O 0.26 0.10 0.08 0.111
> CaO 0.35 0.16 2.28 0.371
> MgO 0.63 0.31 0.82 1.326
> Fe2O3 9.62 1.34 7.82 11.789
> TiO2 1.14 1.06 0.93 0.841
> P2O5 0.06 0.03 0.11 0.128
> MnO 0.01 0.00 0.03 0.029
> LOI 4.73 4.4 7.83 5.35
> total 99.55 99.80 98.93 99.28
>
> As you can see (you can ditch the LOI and then normalize to the total value
> if you want; I just took the numbers as given, for ease and simplicity),
> the Si is very low in your sample, and the Fe is very high. So is the Mn.
> Moreover, your analysis shows no Na, K, Mg, or Ca. Also, the analyses of
> "the real stuff" don't show any V or Zr at all. ...All of which tends to
> suggest that your items are not all that likely to be from Yixing.
> (I have also heard that there is relatively little actual Yixing ware
> available at modest prices in the US, and that most of what you see that
> is readily affordable comes out of Taiwan; but I don't really know how
> accurate that is.)
>
> The fact that it appears to lack alkali metals and alkaline earths strongly
> suggests that it is not clay. That being the case, I have no least clue
> _what_ the hell it is, nor where it comes from. (As far as I'm aware, the
> Taiwan stuff _is_ clay; but I don't think I've seen any analyses, so maybe
> it's crucially weird or something.)
>
> > I'm guessing it is real yixing from the high iron content but I am curious
> > what iron salt is actually in there.
>
> For that, you probably want XRD and a real expert.
>
> > The detectable lead content is probably worrisome to somebody.
>
> (Glad you put "to somebody" at the end of that. 0.02% is probably not
> a big deal, especially if you aren't in the habit of putting OJ or wine
> in your tea and then leaving it in the cup for a day or two.)
>
> > But what is with the titanium? Does it just come along for
> > free with the alumina?
>
> I have never seen a clay analysis that didn't have some Ti in it.
> It probably goes along with Fe rather than Al, but don't quote me.
>
> I have also never (AFAICR) seen a clay analysis that didn't have any
> NaK or CaMg, so if this can be demonstrated to be fired clay, I will
> assuredly want to hear about it.
>
> > The stuff definitely does have some magnetic properties; it will change
> > inductance of a coil if it's in the middle, like a ferrite.
>
> Hum. That is a matter of some interest.
>
> http://newscenter.lbl.gov/2014/05/14...inese-pottery/ =
> <http://newscenter.lbl.gov/2014/05/14/rare-iron-oxide-in-chinese-pottery/>=
That is all.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."