Tea (rec.drink.tea) Discussion relating to tea, the world's second most consumed beverage (after water), made by infusing or boiling the leaves of the tea plant (C. sinensis or close relatives) in water.

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Old 20-02-2015, 02:22 AM posted to rec.food.drink.tea
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Default Yixing Ware

So, my parents gave us a set of yixing teaware for Christmas, labelled
"Tang Chaoxing Purple Teapots." They smelled right, the color seemed
right, but I really don't have any idea how to tell if this stuff is real
or not.

So... I took it into work and asked the mass spectro guys to put it in
the machine. They did, and they got this out:

Element % +/-
------- ----- ----
Si 46.08 0.19
Fe 28.31 0.19
Al 21.72 0.20
Ti 2.05 0.14
Mn 2.22 0.06
V 0.22 0.06
P 0.20 0.01
Zr 0.16 0.00
Pb 0.02 0.01

This resulted in all of the nondestructive testing people hanging out and
asking "what the hell IS this?" I'm guessing it is real yixing from the
high iron content, although now I am really curious what form of iron salt
is actually in there. The detectable lead content is probably worrisome
to somebody. But what is with the titanium? Does it just come along for
free with the alumina?

Anyway, I found this interesting and if this helps anyone else identify
yixing ware, feel free to use 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. The ND guys kept asking if it was actually a
ferrite. I'm not sure what to say...
--scott


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"C'est un Nagra. C'est suisse, et tres, tres precis."

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Old 27-02-2015, 11:58 PM posted to rec.food.drink.tea
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Default Yixing Ware

On 2015-02-20 01:22:21 +0000, Scott Dorsey said:

So, my parents gave us a set of yixing teaware for Christmas, labelled
"Tang Chaoxing Purple Teapots." They smelled right, the color seemed
right, but I really don't have any idea how to tell if this stuff is real
or not.

So... I took it into work and asked the mass spectro guys to put it in
the machine. They did, and they got this out:

Element % +/-
------- ----- ----
Si 46.08 0.19
Fe 28.31 0.19
Al 21.72 0.20
Ti 2.05 0.14
Mn 2.22 0.06
V 0.22 0.06
P 0.20 0.01
Zr 0.16 0.00
Pb 0.02 0.01

This resulted in all of the nondestructive testing people hanging out and
asking "what the hell IS this?" I'm guessing it is real yixing from the
high iron content, although now I am really curious what form of iron salt
is actually in there. The detectable lead content is probably worrisome
to somebody. But what is with the titanium? Does it just come along for
free with the alumina?

Anyway, I found this interesting and if this helps anyone else identify
yixing ware, feel free to use 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. The ND guys kept asking if it was actually a
ferrite. I'm not sure what to say...
--scott


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.

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.

Thanks for the post.

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Old 01-03-2015, 07:05 PM posted to rec.food.drink.tea
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Default Yixing Ware

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."
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Old 16-03-2015, 06:52 AM posted to rec.food.drink.tea
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Default Yixing Ware

Very interesting post. Thanks a lot.

I would like to obtain some of the "real deal" but I am afraid that it
is going to be difficult to obtain. Keeping my eye on TAS and local
thrift stores seems like about all I can do short of prying the wallet
open to the tune of several hundred dollars.



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