[Clayart] white clay leaks.

Ric Swenson ricswenson0823 at hotmail.com
Mon Jul 12 09:30:57 UTC 2021


There is kaolin based high fire (>cone ten...to 15) It contains no iron or other colorant oxides and fires pure white. The word porcelain comes from the Portugese for a pure white shell found on the beaches in Portugal "the porcelana". When they first shipped porcelains from Jingdezhen, China in the 16th century, they marveled at how white it was and called it porcelana.It was translucent and had zero water absorbency. It was fired in large clay saggars in wood fired kilns so no ash could contaminate the glaze surface. When asked where it came from they answered by mispronouncing Chang'nan as China which became the common European names for China and china. Chang'nan was the original town name for what we now call Jingdezhen. During the reign of the emperor at that time the dynasty: JINGDE and the word for 'town'....Zhen, gave us Jingdezhen. Most of the millions of wares exported during that time were blue and white dinnerwares. The emperor loved the wares so much that he had the name of the town changed. It is described in a Chinese saying : "Jingdezhen porcelain is white as pure jade, thin as paper, sounds as a bell and bright as a mirror."

Porcelain can now be made in many countries because of mining expertise. In 1004 AD, the folks in Gao Ling (where we get the name Kaolin now), near present day Jingdezhen, discovered a mountain of pure primary clay which is the basis of porcelain. Secondary clays "travel" and pick up impurities like iron.

There is white stoneware which fires at moderately high temps....cone 5-10 usually have 1-2 % absorption, usually toothy and opaque... and talc clay bodies which fire white but at lower temps, have little vitrification and thus have water absorbency of 2-5 % or more...unless glazed... and can leak.

Your mileage may vary.

Regards,

Ric


________________________________
From: Clayart <clayart-bounces at lists.clayartworld.com> on behalf of mel jacobson <melpots at mail.com>
Sent: Monday, July 12, 2021 10:41 AM
To: clay art <clayart at lists.clayartworld.com>
Subject: [Clayart] white clay leaks.

there is a very old saying.. porcelain is a white body, but, not all white clay bodies are porcelain.

one day we will go to a big show and the potter will be showing cone 013 raku "ta dah" Porcelain...To even suggest
the word "Porcelain" would mean to me that the work is cone 10-12.  It is totally vitrified, and will hold
acid.   So much of what the vendors sell is "fluxed up" white clay bodies and lets face it, no one really
cares if it is "almost vitrified"  I know, semantics

That is why the clay I started using is brown, and totally vitrified. you control the color, the redart
is the flux and makes it more workable.  I swear that in 2095 potters will be complaining their
cone 6 "porcelain leaks". hell, it is not even very close to "white stoneware".

I sat a tall tumbler out of mel 6 clay on Mike Meyers (MN Clay owner) desk and filled it with water.
I said "keep it full for a month." he did.  not a drop of water on his desk.
 I boiled  bars of  clay for  3 hours
weighed them with a digital  scale.
  perfect.
  MEL


website: www.melpots.com<http://www.melpots.com>
www.melpots.com/CLAYART.HTML<http://www.melpots.com/CLAYART.HTML>

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