Mar 1st 16 11:27 am
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Celadon vs. Porcelain

by ahasja » Mar 1st 16 11:27 am

I want to buy a new Gaiwan. Until now I just used a glass-Gaiwan for Silver Needles and a porcelain-Gaiwan for my Taiwanese Oolongs. As the last one fell down yesterday I was looking in different shops and the more I look the more I like the celadon-Gaiwans. Does celadon has any disadvantages compared to porcelain?

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Mar 1st 16 12:16 pm
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Re: Celadon vs. Porcelain

by chrl42 » Mar 1st 16 12:16 pm

I personally perfer white teawares (porcelain) for any type of tea, it helps me to appreciate the color of tea soups, it's how they chinese thought of a white teaware as a prime choice ever since the beginning of loose-leaf brewing as Ming dynasty..I think that's how Jingdezhen and Dehua went on top of a game along with that.

But man..there are just too many kinds of teawares that are needed for anyone that needs :lol:

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Re: Celadon vs. Porcelain

by ethan » Mar 1st 16 2:10 pm

ahasja, I feel thickness is the issue. Most celadon is thicker-walled than most porcelain. My celadon was called stoneware by the people selling it. Thicker means slower to pre-heat & longer to lose that heat; also, it means more weight. Since I have broken several gaiwans & a couple of teapots, I think about ease of handling as part of my decision-making. As someone already replied, you might "need" both.

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Re: Celadon vs. Porcelain

by LouPepe » Mar 1st 16 2:35 pm

I think celadon with puer, liu bao, and high ox/roast oolongs works nice. Preferably if the gaiwan is 'flatter' though. The tall xu de jia celadons can beat your tea up if you don't have absolute control of water temp. But, shou is always an exception.

I like celadon for cha hai, chawan, and tea cups which you want heat to be retained. Porcelain is nice for cups you want cooled quicker. But in the end, the function, beauty and aesthetics of both are much needed in anyone's collection :-)

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Re: Celadon vs. Porcelain

by William » Mar 1st 16 2:50 pm

Generally speaking, celadon increase the aftertaste, BUT, depending on the amount of iron oxide present inside the glaze, the increase can be light or drastic. Most often, with heavy presence of iron oxide, the body of the tea can be felt somewhat more thin and subtle.

Usually, esthetically speaking, bluer means lighter presence of iron oxide, while a dark green colour means heavier presence of iron oxide.

Mar 1st 16 4:37 pm
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Celadon vs. Porcelain

by ahasja » Mar 1st 16 4:37 pm

Thanks you so much for the answer and information. So I need to buy two gaiwans. ;)

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Re: Celadon vs. Porcelain

by William » Mar 1st 16 4:56 pm

ahasja wrote:Thanks you so much for the answer and information. So I need to buy two gaiwans. ;)
Or just use different cups! :wink:

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Re: Celadon vs. Porcelain

by Bok » Mar 2nd 16 2:22 am

I am confused, isn’t Celadon a glaze type rather than a material???
Celadon vs Porcelain as a sentence does not make sense to me.
Should be Celadon vs Other glazes

Celadon can be applied to clay and porcelain, thickness should not be the issue… I have some tiny antique wine cups with Celadon glaze over porcelain and they are really thin!

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Re: Celadon vs. Porcelain

by Tead Off » Mar 2nd 16 2:50 am

Bok wrote:I am confused, isn’t Celadon a glaze type rather than a material???
Celadon vs Porcelain as a sentence does not make sense to me.
Should be Celadon vs Other glazes

Celadon can be applied to clay and porcelain, thickness should not be the issue… I have some tiny antique wine cups with Celadon glaze over porcelain and they are really thin!
Yes. Celadon is the glaze that is used over porcelain. Most porcelains we think of are clear glazed so they remain white. Celadon is colored, green/blue.

What I have noticed is more of a difference from clear glazed porcelains compared with unrefined porcelain that still has some iron in it. These give a noticeable difference in flavor from the pure white variety. The pure white variety was probably developed for the nobles.

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Re: Celadon vs. Porcelain

by ethan » Mar 2nd 16 4:07 am

Yes, TeadOff & Bok; however, around Chiangmai potters do an extra wetting, pressing, & drying of the clay which adds density, weight, & thickness (not strength, I once bought 4 dinner plates & 2 broke in transit). Technically, I may be wrong but think of this thick ceramics as stoneware, not porcelain.

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Re: Celadon vs. Porcelain

by Bok » Mar 2nd 16 4:12 am

ethan wrote:Yes, TeadOff & Bok; however, around Chiangmai potters do an extra wetting, pressing, & drying of the clay which adds density, weight, & thickness (not strength, I once bought 4 dinner plates & 2 broke in transit). Technically, I may be wrong but think of this thick ceramics as stoneware, not porcelain.
Well technically, thinness does not matter as to what it is called. The compositio matters.

But with porcelain a thinness, which is not achievable with other clays, is possible.

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Re: Celadon vs. Porcelain

by .m. » Mar 2nd 16 8:00 am

What exactly is celadon? This term seems to be applied by people to anything with a greenish/blueish glaze. The differences between these glazes are often striking. Modern celadon (as in celadon gaiwans) seems to be a very different animal than the antique pieces...

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Re: Celadon vs. Porcelain

by Midwinter_Sun » Mar 5th 16 5:48 pm

.m. wrote:What exactly is celadon? This term seems to be applied by people to anything with a greenish/blueish glaze. The differences between these glazes are often striking. Modern celadon (as in celadon gaiwans) seems to be a very different animal than the antique pieces...
You are absolutely right, today this term seems to be applied by people to anything with a greenish/blueish glaze.

Without a lab test, you cannot tell what is in the glaze based on the color, as modern glazes have very little to do with the celadon of old.

Originally this color, reminiscent of fine jade, was produced in China by the means of firing glazes with a small amount of a specific iron oxide glaze in reduction ( controlled diminished supply of air, and thus oxygen, to the kiln ).

The reason original celadon was so highly prized and considered the standard of porcelain for generations was the amount of craftsmanship required to produce the glaze. One truly had to be a master of fire.

Today, modern glazes fired in electric kilns will contain copper oxide or any other number of ingredients chosen for color stability and ease of use.

As for the head topic, I am a firm believer that one has to try many options to find what fits you.
I enjoy iron oxide glazes, celadon and non-celadon, when drinking city water brewed tea.

As I live in the country and my well water is very tasty and very rich in Iron, teaware influence on the taste of my teas is minimal, so I concentrate on the Joy factor of teaware :mrgreen:

So perhaps before discussing teaware one has to consider the water.
Have you tasted your water after boiling, from a clean glass? In my humble opinion, depending on the taste, you might consider filtration or other adjustments first, as the water factor is much more pronounced than teaware.

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Re: Celadon vs. Porcelain

by JBaymore » Mar 5th 16 7:14 pm

The celadon color range (from ice blue to a deep green when on a white ground like porcelain) in the "real thing" comes from a VERY small percentage of iron oxide that is in the glaze. The favoring of the green versus blue tones is based upon the molecular chemistry of the general glass matrix into which the iron is included.

The traditional glaze is fired in a reduction atmosphere in the low to mid range of the typical high temperature firing (end point in the 2300 - 2400 F range). Before about 1500F and after about 2200 F the atmosphere of the kiln chamber environment typically has no impact. This changes the oxidation state of the iron to the reduced phase and alters the color rendition from the typical "yellow" that one would get out of small inclusions of iron in an oxidation firing. The "yellow celadons" you might see in museums are the same glaze as the greens/blues..... just fired in oxidation.

One of the "secrets" for a really good celadon glaze that more closely resembles the jade qualities of the Chinese originals is the inclusion of a very trace of phosphorous pentoxide in the glaze melt. P2O5 is immiscible in silica glass, so it causes refractive index changes as light penetrates the glaze layer ... giving a bit of a depth to the color.

Traditionally this P2O5 was coming from the traces of it contained in wood ashes, that were used to supply a good portion of the main calcium oxide (CaO) flux that the typical Chinese celadon glaze uses. There are also sodium and potassium oxides present as secondary fluxes,... and the amount of these can affect the color shift between blues and greens. The type of clay added to the glaze base batch also influenced the color rendition. because titanium dioxide impacts the color shift also, and some kaolins contain more TiO2 than others.

The typical percentage addition to a base glaze batch is from 1/2% to 2% by weight of red iron oxide (Fe2O3) into the glaze. Sometimes the iron content for a celadon glaze is supplied by iron that is contained in other raw materials that make up the glaze batch.... like an iron bearing clay. The number of mols of iron oxide in the glaze matrix is typically only from about 0.015 to 0.047 of a mol........ a miniscule amount when compared to the typical 5.5 mols of the base glaze.

There is so little iron in the overall glaze, and the typical celadon glaze formula is so typically chemically stable (from leaching), that I cannot see in any realistic way in how it could possibly impact the qualities of the tea no matter which oxidation state the iron might be in.

best,

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

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Re: Celadon vs. Porcelain

by William » Mar 5th 16 9:36 pm

JBaymore wrote: There is so little iron in the overall glaze, and the typical celadon glaze formula is so typically chemically stable (from leaching), that I cannot see in any realistic way in how it could possibly impact the qualities of the tea no matter which oxidation state the iron might be in.

Still I feel an extreme and deep impact on teas when celadon is used .. maybe Im going crazy, possible after all!