Talk:Porcelain

I'll apologise in advance for the long process of filling in this article. My source material is in Chinese. I don't read Chinese very well, so translation is painfully slow. -- Michael 09:18 26 May 2003 (UTC)

It occurs to me that I'm going to need someone with more knowledge to fill out the "techniques" section. I can barely decode what the works I'm reading are babbling about when it's not technical language. Technical language goes way over my head. -- Michael 09:24 26 May 2003 (UTC)

It seems that this article is trying to serve several purposes. 1) to discuss the clay body known as porcelain and its history. 2) to discuss the use of the clay body in historic ware, particularly in China. 3) to discuss the use of the clay body in figurines and slipcast ware, both in Asia and Europe.

I would like to add information about the history and development of porcelain pottery forms, primarily on the potter's wheel. This would cross reference with Chinese and Japanese history and art as well as the pottery tree I am working on. English pottery/porcelain in an industrial setting would be addressed as would modern studio/art porcelain ware. Any comments would be welcome on how to divide this information and develop interlocking articles. -W. (an anon) 02-14-05 now logged on as WBardwin 06:50, 19 Feb 2005 (UTC).

If I may I would like to add my comments to the above:

“Porcelain is a ceramic material made by firing China clay and China stone” Porcelain is made using many other materials than China stone. The latter is a rock specific to one area of Cornwall in the United Kingdom. Presently extraction of this is very limited

“Porcelain wares may be formed by moulding, by hand-building and in the case of round-wares, by throwing on a potter's wheel.” Many other shaping process are used

“Further weathering of China stone changes its mineralogy to form China clay.” Is a little simplistic as China stone will never become china clay

”Kaolin is a platy mineral” Kaolin is a rock and not a mineral. However it is a rock rich in the mineral kaolinite

“ ...residual clays (kaolin /china clay) ... Sedimentary clays ... like bentonite” Kaolins are found that are both primary and secondary, or residual and sedimentary

“Porcelain -- almost 100 % china clay” This could be read that a porcelain body is comprised of all entirely china clay whilst many formulations do not exceed 50%

“China stone (petuntse or baidunzi) is actually feldspathic. Nowadays it's generally held to be micaceous.” China stone is not the same as either petuntse or baidunzi. All do however contain mica, feldspar and kaolinite Kind regards, Andy

New material

If no one objects, I'm proposing to re-write the definition of porcelain along these lines.

Porcelain is a ceramic material made by firing China clay and China stone in a kiln at temperatures in the region of 1200 to 1350 degrees Celsius. The resulting material is hard, strong, glassy and durable, but is also brittle. It is white or off-white in colour. As defined in the West porcelain is translucent.

The components of porcelain are China clay (kaolinite) and crushed China stone (a form of feldspar). Both are found in nature and result from the weathering and decomposition of igneous rocks such as granite and basalt.

Porcelain has many industrial uses and is also employed to form wares ranging from everyday household crockery to objects of fine art. Porcelain wares may be formed by moulding, by hand-building and in the case of round-wares, by throwing on a potter's wheel.

Porcelain wares are usually coated with a layer of glaze and are often decorated with coloured enamels.

Comments, anyone? --N.Hopton 19:21, 7 November 2005 (UTC)[reply]

Thanks for the new material -- I shuffled things a little bit, moving the technique section up and combining some old and your new information. Feel free to move things around again, if I didn't get things in an acceptable order. Always glad to see new clay people on Wiki. If you are interested, we are sporatically discussing an organizing method for clay and ceramic related articles on the Pottery talk page. Best wishes. WBardwin 21:22, 7 November 2005 (UTC)[reply]

Hi, it's Nick, by the way. I've just added a few lines about Chinese porcelain. To be honest, these are a bit of a dog's breakfast but I'll tidy them up as I go along.

Just a quicky, what does this mean? "...and that it tends to continue to 'move' for longer than other clays, requiring experience in handling to attain optimum results". That it takes longer to dry out and stays plastic for longer? Greater drying shrinkage and increased likelihood of cracking? Not a potter myself, as you can tell <g>.

Nick. --Nick 15:48, 8 November 2005 (UTC)[reply]

a little clay jargon, I'm afraid. Thanks for the query -- we sometimes forget that obvious things are not obvious. The differences between porcelain and stoneware pottery include particle size, the size of spaces between the particles, and the purity of the clay mix. Porcelain clay is derived from residual clay, where feldspathic rocks break down "in place" forming large secure beds. Since the material is not moved about by wind and water, friction has little bearing on the formation of clay particles. The particles remain large and the beds are quite porous because water can move between the layers of flat clay particles. In contrast, sedimentary clays are displaced by moving water or wind, and become mixed with organic material and non-feldspathic rocks and minerals. Friction has a strong influence and particle sizes are smaller, sometimes very small. Clays with smaller particles are more "plastic" -- more stretchable and malable. Large particles in a clay body allow clay to absorb water quickly, and reduce the clay's structural integrity as the potter is creating a piece. Large particles have more inertia, so as the wheel slows the particles try to move at the earlier faster rate for a longer time than small clay particles. Stoneware potters call the small particle, plastic clay they work with "more forgiving," because it allows them to work with more speed and to correct errors more easily. Porcelain bodies, even some of the more carefully designed chemical blends, can be a real challenge for a production potter.

Nick, if this explanation makes any sense to you --- please ask lots of questions --- I'll try and refine it to go into the article. Comments please. WBardwin 06:25, 10 November 2005 (UTC)[reply]

Thanks for this, WB. Just to get things straight in my own mind, then. China stone results from the weathering of a parent igneous rock and is found close to the parent rock. Because it has not moved far from the parent rock it remains largely uncontaminated. Further weathering of China stone changes its mineralogy to form China clay. This is easily washed out by the elements and may be deposited some distance away from parent rock. In the process of being transported in this way China clay may become contaminated to a greater of lesser extent by other materials. How does this sound?

Regarding the tendency of porcelain clays to 'move', I'm still not sure that I grasp this, it's obviously important but I can't see why. Forgive me. Kaolin is a platy mineral of small particle size right enough and it can hold a lot of water, on the surface and internally. Because the clay platelets can align themselves and slip over each other easily under pressure (from, say, the hand of the potter) does this mean that they 'move for longer'. Sorry to be so thick.

Nick. --Nick 11:55, 10 November 2005 (UTC)[reply]

Nick -- The movement imagery is probably connected to particle size. In Physics, "an object at rest tends to stay at rest unless acted upon by an outside force." Potters find this to be true with clay. Clays with fine particles, the finer the better, respond more promptly to the pressure and manipulation of the potter's hands and the speed of the potter's wheel. Clays made up of large particles -- the finest porcelains -- resist this manipulation to a surprising degree. The same rule holds as the potter slows down the wheel at the end of the construction process. As the wheel slows, the fine particles slow at a noticably faster rate. With porcelain, it is important to decrease the rate of speed more slowly, over a longer period of time. If you aren't careful, the larger particles will still try and whip around the center of the wheel -- in orbit, if you will. The tendency then, is for the piece to warp slightly on the wheel and then continue to warp in the same direction as it is dried and fired. Any help????

on a second topic, in the article (not Nick's contribution, I believe), it states that porcelain is unique in that it is often once fired. I'm afraid that's not really the case. Most historic pottery -- Asian, European, Native American -- was "once fired". It was the most economical and least labor intensive way of working. It is only when we moved toward industrial methods, and broke the process into stages, that people began using a bisque firing. The longer process allows many stages of decoration and several layers of colorants, glazes and enamals. Bisque firing also reduces losses in each kiln and so increases the potter's output. Some industrial produced wares go through three or four firings, all at different temperatures. Modern potters, again in Asia, Europe and the US, adapted the industrial process to allow themselves more creativity as well. If no one has any objections --- I'll try and come up with a couple of sentences to correct the article's error. Comments welcome. WBardwin 03:02, 11 November 2005 (UTC)[reply]

Hi WB, in fact that was me that wrote the stuff on Chinese porcelain. I didn't say that once-firing was unique to China, just that Chinese porcelain is unusual because it was (and is) in the main once-fired. I know that many ceramics like the ones you mention were once-fired but I'm not sure how many of these would fall into the category of porcelain.

I'm interested in your comments about the finest porcelain wares being made with a body material containing large particles. What would these larger particles be? Frit, grog or something similar perhaps, to provide internal restraint against shrinkage? Anyway, I'll lay off this side of things for the time being and concentrate on my Chinese stuff <g>. Nick --Nick 13:10, 11 November 2005 (UTC)[reply]

Yup, Korean, Chinese, Japanese porcelains all started off being once fired. People couldn't afford the fuel and manpower required to do multiple firings. Traditionally oriented potters (I am not certain about the new Chinese porcelain factories) in Asia still once fire, although in some anagama kilns a front or side chamber that doesn't get as warm as the inner chambers may be intentionally used for bisque ware. When Europeans (first the Dutch, then the British) tried to steal porcelain technology (even though they had limited supplies of kaolin/china clay and ended up with a dirty grey porcelain), they once fired too. Bisque firing emerged in about the 18th century, in Europe.

The larger particles are just the clay particles -- all clay exists in microscopic flat plate shaped particles, but the residual clays' (Kaolin/china clay) particles are comparatively large because they have been subject to minimal erosion. Sedimentary clays, usually grey/brown clays like bentonite, have been eroded to the point that the average particle size is very very tiny. So, stoneware clays made from the tiny particles are denser, easier for the potter to manipulate, more forgiving in handling, more plastic, and have more inherent strength as they dry. Porcelain -- almost 100 % china clay with those big clay particles with more mass per particle -- has more open space within the clay. Those spaces fill up with more water at a faster rate. Consequently, the clay rapidly becomes softer to work with, has less wet and dry strength, and the big particles slide around in the water ("move") when placed under tension by the potter's hands and speed of the wheel.

Korean potters historically experimented with grogs and additives to try and reduce their "loss" due to porcelain's inherent characteristics. They also threw stoneware bodies and covered them with coatings of a thick porcelain slip. And, of course, modern industrially created porcelains address some of these concerns. Some actually grind the porcelain particles (in a clean environment) to make them smaller and the body stronger, while others add grogs.

Nick, don't give up on me now!! I need your perspective. I know it's kind of boring, but if we can come up with an explanation a "non-potter" can visualize, then we can put it in the article. Comment when you have the time, please. WBardwin 17:14, 11 November 2005 (UTC)[reply]

"Korean, Chinese, Japanese porcelains all started off being once fired." Yes, but wasn't the reason for this that porcelain was introduced into Korea and Japan by ex-pat Chinese potters? This was certainly the case in Japan. I'm not quite sure about your comments on clay particle size. The important thing is that kaolinite and the smectites (like bentonite) are different from one an other in mineralogy, the smectites for example have much greater internal surface area, hold a lot more water and shrink a lot more than the kaolinites. It's not just a question of particle size. But I'm no expert here and might well be wrong, I hasten to add.

When potters talk about 'loss' do they mean 'drying shrinkage'? Or does it just refer to the number of duds in a firing?

Regards, Nick. --Nick 11:38, 13 November 2005 (UTC)[reply]

As far as I know, historic people "once fired" -- no matter what their clay material - porcelain - stoneware - earthenware. Just too expensive in terms of fuel, time and effort to do otherwise. I used most above because someone I've not heard of might have used a bisque or preparation firing. Korean potters actually used some porcelain (although porcelain beds are more rare in Korea) before the Chinese influenced the forms and methods of the clay's use. As for the Japanese, they were late bloomers and literally stole all their clay technology and, during one war, Korean potters as well. In mineralogy, I bow to your expertise - I just use the stuff. But in terms of the mechanics of throwing pots, the particle size/characteristics and ratios in composition of the clay change the way clays respond to the potter's hand. A porcelain, with such a high percentage of kaolin/china clay particles, "moves" and responds differently to water application and pressure from the potter and speed of the wheel.

Loss. I used it in terms of duds per firing, but potters are very aware of drying shrinkage and must take it into account while throwing and producing ware. The rate of drying and shrinkage has an impact on loss as well, as pots are often lost in the green state if the potter is not attentive. WBardwin 16:47, 13 November 2005 (UTC)[reply]

Once again, thanks for this. I'm doing a bit on the Chinese side of things at present and I would be very grateful if you and some of the other potters would give this a good going over. Nick --81.86.134.253 19:35, 13 November 2005 (UTC)[reply]

Hi WB, I see you're having fun knocking out the commercial links that keep appearing in the article <g>. Quite right too. Gotheborg.com is a difficult one because it is the best site on the Internet for information on Chinese ceramics, but it does have some commercial content and this is why I have avoided posting links to it in anything I've written. A pity, because they have a version of Tang Ying's memoir that is better than the one at Seattle, but rules are rules. Regards, Nick. --81.86.134.253 10:41, 24 November 2005 (UTC)[reply]

Nick -- could you select an apt quote or two from Tang Ying's memoirs on the site to incorporate into the article? By tying an external link to that part of the site, rather than putting it in the links section, we could bypass much of the commercial concern on Gotheborg.com. But, commercial links are always showing up all over Wiki -- I'm sure it looks like free advertising space!! Best...........WBardwin 16:40, 24 November 2005 (UTC)[reply]

Come on then, WB, I'm knocking my socks off here on the Chinese side, how about doing a bit in the European department <grin>. Actually, I'd appreciate it if you'd give my Chinese stuff a going-over too. I'll be doing a bit on Qingbai in the near future.

Hi WB, All, as you'll have seen, I've done just a couple of paragraphs on the European discovery of porcelain, is this OK? It's not something I know much about. Could you do a bit on the different types of European porcelain, hard paste, soft paste, et cetera? Can you think of anything I ought to be doing? BTW, I see that you're interested in the Ancestral Puebloans. We were around the Mesa Verda a couple of months ago and found those black on white ceramics quite remarkable. They used dinosaur gastroliths to smooth them! See you soon, Nick --81.86.134.253 18:42, 14 December 2005 (UTC)[reply]

Nick - both my work and holiday schedules are tight for now, but I have a couple of good sources on European porcelain and imitation china ware that I can draw on after Christmas/New Years. Yes, I have experience in archaeology, did some survey work in the Four Corner's area some years ago, particularly in Hovenweep National Monument. Wonderful ceramic traditions throughout the region and beautiful craftsmanship with some very difficult clay. Southwestern clay is a gritty earthenware with lots of mineral content. It has to be very carefully prepared and fired. Thanks for your effort. I think I should bulk up the porcelain production process, as well. Happy Holidays! WBardwin 22:51, 14 December 2005 (UTC)[reply]

We missed Hovenweep unfortunately. Anyway, looking forward to pushing on with the good work after the holidays. Wishing you and yours a very merry Christmas and a happy new year. Regards, Nick --81.86.134.253 19:27, 16 December 2005 (UTC)[reply]

Chinese porcelain is made from kaolin and a form of feldspar called petuntse. The trouble is that I'm not so sure that China stone (petuntse or baidunzi) is actually feldspathic. Nowadays it's generally held to be micaceous. Any ideas anyone? Regards, Nick.--Nick 16:57, 7 January 2006 (UTC). OK, I've re-written this to reflect current thinking. Regards, Nick. --Nick 20:54, 10 January 2006 (UTC)[reply]

External links

I posted a link to a nice site on fine china and dinnerware. This site has some very good information not found elsewhere on the net. It was not a commercial site as they only provide information. Choosing Dinnerware and China

When I removed the link -- it seemed to me to be an aid to selecting and buying specific types of china and porcelain ware. Information provided was oriented toward purchase and ownership, rather than toward "knowledge" and information. So what do you think? Should it be restored? WBardwin 07:56, 7 January 2006 (UTC)[reply]

Interesting. That is why I put a Fine China (external link L2 Headline) title for it. I am not sure right now as there is little fine china and dinnerware information on wikipedia at this point. Let me get back to you. Maybe we need to write a new page on types/grades of fine china and uses, as right now searching wikipedia for fine china redirects me to porcelain which I believe is not the exact same as fine china per se.

Still not happy with definition

I'm still not entirely happy with the definition of the term porcelain at the very start of the article. I'll post a proposed re-wording here in the next couple of days, for comment. --Nick 20:54, 10 January 2006 (UTC)[reply]

Need some help with porcelain terms

For WB, happy new year. Anyone: do they still talk about porcelain clays being 'long' or 'short' according to plasticity and are porcelains still 'soaked' in the kiln to encourage the growth of mullite? Regards, Nick. --Nick 20:54, 10 January 2006 (UTC)[reply]

Yes, to both questions. But commercial porcelain bodies are being improved all the time in an effort to reduce their throwing and firing flaws. Happy New Year to you too. WBardwin 05:04, 11 January 2006 (UTC)[reply]

Draft definition of porcelain, for comment

Ok, I've made the changes that I posted here. The other day I reverted the work of an anonymous editor, which I really shouldn't have done and I apologise. I'll go through what he posted and incorporate it where possible. I'll also add a bit on China stone and the feldspar question. As for changing China stone to petunse I just don't know, let's talk about it. Regards, Nick.--Nick 12:15, 15 January 2006 (UTC)[reply]

sorry I haven't had much Wiki time to actually edit, things are hectic and disjointed in the real world at the moment. I did pull out my books and will try and incorporate some potters viewpoint into your definition asap. YOu are doing a great job. WBardwin 03:53, 16 January 2006 (UTC)[reply]

Thanks for the kind words. Having retired, I don't live in the real world any more, I'm pleased to say <g>. I'd like to do some more on terminology, because this is very confusing to many people, including me (potters call stuff clay that isn't clay, et cetera. Or not clay as defined by mineralogists). --Nick 10:36, 16 January 2006 (UTC)[reply]

Pressing on

There's a lot of good stuff on terminology and techniques over in the article on Pottery. Rather than duplicate this on the porcelain page I think it would be best to put in some links to the pottery page, where appropriate and delete anything that isn't specifically concerned with porcelain. I'll do this in the next day or so, unless anyone objects. --Nick 11:43, 21 January 2006 (UTC)[reply]

Just on the moving thing, I don't want to get this wrong. So, when you're working a lump of clay on the wheel it moves under your hands. When you take your hands off, it begins to stiffen (it's thixotropic) but this stiffening can take longer with some clays, like porcelain clays, than with others? Sorry, even my mother used to say that I'm as thick as two short planks <g>. --Nick 19:09, 21 January 2006 (UTC)[reply]

"moving" - involves the laws of physics as well. As the wheel turns, all the clay/mineral particles go "into orbit" around the center of the wheel. Pressure from the potter's hands determines the diameter of the orbit, the thickness of the clay and so the shape of the pot. But -- if the potter stops the wheel abruptly, or removes his/her hands abruptly, the particles try to keep moving in the established order at the established rates. Even when the potter slows everything down, gradually, before completing the pot, the particles keep trying to move on. The larger particles characteristic to porcelain are particularly stubborn, as their size gives them greater mass. So porcelain ware "warps" at a higher rate than stoneware, and potters see more loss in the final firing. So, in general, greater skill is needed to be a porcelain potter and many Chinese, Korean and Japanese potters deserve to be revered for their technical mastery of the difficult material. On your retirement, I'll stop feeling guilty about not being able to keep up with you. Hope you are having fun. WBardwin 22:42, 21 January 2006 (UTC)[reply]

I think I might be on the way to understanding this, it ties in with some other points about throwing that might be worth mentioning in the article. I'll dolly this up, but put roughly: WB sits at his wheel, centres a lump of clay, opens it up and starts to pull the walls of a pot. Except that he's not doing any pulling, because you can't pull clay, it breaks. What he is doing is compressing the clay between his fingers and the clay starts to move outwards, but WB controls this by guiding it with his hands. When he's finished he takes his hands off the pot and starts to slow the wheel. But the pot wants to keep on turning and if the wheel is slowed too quickly the pot twists (it's trying to turn faster than the wheel it's stuck to). It can do this because the clay is still plastic and capable of "moving". This "movement" can cause warping not only on the wheel, but also during drying and firing (during drying and firing the pot tries to "unwind"). I was reading something the other day about "plastic memory" which might fit in here. Is what I have written above anywhere near right? Thanks once again for helping a non-potter. --Nick 20:00, 25 January 2006 (UTC)[reply]

If I may I would like to add my comments to the above:

“Porcelain is a ceramic material made by firing China clay and China stone” Porcelain is made using many other materials than China stone. The latter is a rock specific to one area of Cornwall in the United Kingdom. Presently extraction of this is very limited

“Porcelain wares may be formed by moulding, by hand-building and in the case of round-wares, by throwing on a potter's wheel.” Many other shaping process are used

“Further weathering of China stone changes its mineralogy to form China clay.” Is a little simplistic as China stone will never become china clay

”Kaolin is a platy mineral” Kaolin is a rock and not a mineral. However it is a rock rich in the mineral kaolinite

“ ...residual clays (kaolin /china clay) ... Sedimentary clays ... like bentonite” Kaolins can be primary and secondary, or residual and sedimentary, though of course not the same deposit

“Porcelain -- almost 100 % china clay” This could be read that a porcelain body is comprised of all entirely china clay whilst many formulations do not exceed 50%

“China stone (petuntse or baidunzi) is actually feldspathic. Nowadays it's generally held to be micaceous.” China stone is not the same as either petuntse or baidunzi. All do however contain mica, feldspar and kaolinite

Kind regards, Andy

Hello Andy, pleased to see you here. I think most of what you say above applies to older versions of the article. Taking your point about China stone I know they excavate something called China stone in Cornwall, but I was using the term in the context of Chinese porcelain, to indicate the rock the Chinese call baidunzi. This seems to be what some of the books on Chinese porcelain do. We might call it porcelain rock or porcelain stone, I suppose. I've recently added pressing and slip-casting to the ways of forming, if you have any other methods then please, lets have 'em. Regards, Nick. --Nick 20:59, 31 January 2006 (UTC)[reply]

Hello again Nick, Thanks for the comments, and to respond: The term China stone is specific to the feldspathic material mined in Cornwall. The origin is indirect: after is use to make china which was so called after ware from the country of China. The same material also goes by the name Cornish stone or Cornwall stone; the multitude of names is possibly as a result of its long production now over 200 years. It does sometimes get called petunse, which along with baidunzi, are from different rocks from different locations

Porcelain rock or stone are possibilities but what about Pottery stone. Yes this is not quite as appealing as yours for a porcelain raw material but it is actually what is used by the Chinese themselves these days when discussing the material. It also worth noting that there is not one type and the term is generic

I’ll add a few more shaping processes when time allows

Kind regards, Andy

Hello Andy, WB, I'd settle for porcelain stone if everyone agrees, it's the term used by Kerr and Wood (see reference in the article). The term will only ever appear in the Chinese porcelain section, I should think. Make the changes by all means, as far as I'm concerned. We're away to the sun for a few days, see you in about a week's time. Oh, regarding China stone/porcelain stone; I think Andy might think that this is feldspathic, but it's not (according to the head honcho at Sèvres about a hundred years ago, and a fair number of people since). Let's talk before anyone makes any changes in this area <grin>. See you soon, Nick.--Nick 19:52, 1 February 2006 (UTC)[reply]

Hi Nick, What source do you have for the claim of being non-feldspathic? China stone, to which I refer to the UK material, is unquestionably feldspathic with major accessory minerals including kaolinite, quartz and various micas. The designation of the Chinese rocks is less easy as there are many different deposits: many are feldspathic whilst others are predominantly micaceous. As far as terms ... why only one? If porcelain stone is in legitimate use it of course it should be listed but could other terms not also included. Say petunse in a historic context but also pottery stone as it is in popular use not least by the people digging and selling it

A couple of other comments about the existing entry: 1.Whilst most, but suprisingly not all, bodies for sanitary wares are vitreous these are not categorised as porcelain 2.A small expansion on dental porcelain would be useful that notes modern compositions contain little, if any, clay 3. The effect of reduction in porosity, both open & closed, on translucency should be stressed

Enjoy the sun ... Regards, Andy

Hi Andy, All, the source for the claim that Chinese porcelain stone/China stone/baidunzi is not feldspathic comes from Kerr and Wood, who refer to the work done around 1900 by Georges Vogt, technical director at Sèvres. K&W talk about the feldspathic fallacy. I don't doubt that English china stone is feldspathic and to avoid confusion I'll change the references to China stone to porcelain stone in the Chinese porcelain section. Definitions are Hell. There just isn't a universally accepted definition of the term Porcelain. I mean, how would you define the material that comprises the body of sanitary wares? People use terms like proto-porcelain and porcelaneous-wares, but it's all fudge in the end. I'm not quite sure how voids in the body, open or closed, directly affect translucency. Regards, Nick. --Nick 12:20, 12 February 2006 (UTC)[reply]

Böttger and Tschirnhaus

Traditionally Böttger has been credited with the invention of European porcelain, but the evidence collected (see the extensive references in German site on Tschirnhaus) make this view untenable. Böttger deserves credit for initiating the manufacturing process, but not for inventing the material. Ekem 19:18, 2 February 2006 (UTC)[reply]

Good points. If it's OK with you I'll try and merge your words with mine to make the story flow a little more evenly. Regards, Nick.--Nick 12:23, 12 February 2006 (UTC)[reply]

Hello Nick, Thanks for the response. Whilst not disputing your references there are both micaceous and feldspathic pottery stones being produced & used in China. As far as an accepted definition of porcelain how about those found in: 1. EC Combined (Tarif) Nomenclature 2. ASTM C 242 - 01 Standard Terminology of Ceramic Whitewares and Related Products

Oh dear! I think we'll have to skirt round trade groups, they're just TDD (too damned difficult).

And you asked “how would you define the material that comprises the body of sanitary wares” ... I wouldn’t: sanitaryware is taken as being a separate body type.

I'll bet the people who make it and the people who buy it still call it porcelain. It's just the old problem of definition again. We have to fudge some things because they are just TDD.

And pores ... they are in effect opacifiers, by scattering light, and so they reduce translucency. As a body that will become translucent moves towards vitreous the reduction in number and size of pores is paralleled with the increase in light transmission Kind regards, Andy

I agree with your second sentence, as the body becomes more glassy it becomes more translucent. Regards, Nick.--Nick 11:12, 14 February 2006 (UTC)[reply]

Hi Rick,

Quoting from ‘Dictionary of Ceramic. 3rd edition. Teh Institute of Materials. Dodd & Murfin. 1994.

Porcelain One type of vitreous ceramic whiteware. The COMBINED NOMENCLATURE defines this as: completely vitrified, hard, impermeable (even before glazing), white or artificially coloured, translucent (except when of considerable thickness) and resonant. In the UK the term is defined on the basis of composition: a vitreous whiteware made from a feldspathic body (typified by the porcelain tableware made in Western Europe and containing 40-50% kaolin, 15-25% quartz and 20-30% feldspar.) In the USA the term is defined on the basis of use: a glazed or unglazed vitreous ceramic whiteware used for technical purposes, e.g. electrical porcelain, chemical porcelain etc. Note, however that the term electrical porcelain is also used in the UK The firing of porcelain differs from that of earthenware in that the first firing is a t low temperature (900-1000oC) the body and the feldspathic glaze being subsequently matured together in a second firing at around 1350-1400oC.

Are you OK for putting a new version together to reflect the recent discussions? Any more thought on the Pyrometric cone entry which does need modifying. Also how about joinng the discussion on pottery, stoneware, kilns ... all need tweaking a little but seems to have gone quiet as of late. Kind regards, Andy

Hi Andy, yes, I'll go through the article in the next couple of days to incorporate some of what we've been discussing. Give me a bit of time though, I'm up to ears at the moment. Regards, Nick.--Nick 19:21, 14 February 2006 (UTC)[reply]

Bowling-up

Hi WB, All, this is another dose of fudge, but I'm trying to cover WB's points about moving and bowling-up. What I've written is this: (but I'm not at all happy with it, comments please!)

Short clays, such as those used for throwing porcelain wares, are particularly susceptible to a form of distortion known as bowling-up. When a piece is being worked on a wheel the internal structure of the clay finds an equilibrium that becomes unbalanced as the wheel is slowed and stopped, leading to the development of stresses that can cause warping in the body. Porcelain clays are more vulnerable to bowling-up than many other of the clays used for throwing because they move for longer, which is to say that they stiffen less quickly after working than some other clays. It should be noted that the stresses that develop after working on a wheel can continue to cause problems of warping during the subsequent stages of drying and firing.

Regards, Nick.--Nick 13:36, 15 February 2006 (UTC)[reply]

Hi Nick, I’m confused about your description, and not just that bowling-up is a new term to me ... but as always the medium prevents a conversation in which I’m sure it could be explained and understood. However I wonder if an encyclopaedia is a suitable medium for making faults? I can only think of why a person would refer to such a source: what is porcelain ... sure some technical stuff and historically information but a specific fault? If bowling-up is included then the entire multitude of making faults, and not just those related to wheel making, would seem to have to be included. Of course this would then be a very long article. IMHO I don’t think wikipedia is the place, maybe a reference to a suitable a book could be given such as ‘Ceramic Faults and their remedies’ by Harry Fraser. How about developing your entry into something about plasticity and why porcelain bodies are generally not overly strong in this characteristic? Kind regards, Andy.

Hi Andy, I hope I've taken your comments on board. As you'll see, I've hacked out a lot of words on shaping and moved them to the article on the potter's wheel, changed the references to China stone to porcelain stone and added feldspar to the materials used for making porcelain. Regarding faults, you're right I think, fewer words are needed. Regards, Nick. --Nick 09:40, 23 February 2006 (UTC)[reply]

Chinese porcelain section

All, does anyone have any strong views on keeping the section on Chinese porcelain where it is, or would it be best to move it to an article of its own? Regards, Nick. --Nick 09:40, 23 February 2006 (UTC)[reply]

LAST CALL FOR COMMENTS! If I don't get any feedback on this proposal I'll be making these changes in the next couple of days -- let's say on Wednesday. Regards, Nick. --Nick 18:59, 27 February 2006 (UTC)[reply]

Categories of porcelain

I'll be doing a bit on categories of porcelain next, hard-paste, soft-paste, bone-china, and so on. Any words, definitions, comments, et cetera, would be appreciated. Regards, Nick. --Nick 11:14, 24 February 2006 (UTC)[reply]

I think it’s misleading to include soft-paste as a category of porcelain because it is not porcelain! It’s better treated in a historical section on the attempts outside China to imitate porcelain, with links to separate articles on the more important of these. They all involve low-fired bodies, whether earthenware or frit-ware. The list should include

The Persian frit-wares developed from the 13th century. (See Islamic pottery)
Iznik pottery
Tin-glazed pottery
Lattimo or milk glass and porcellana contrefatta or counterfeit porcelain
The various soft-pastes from the 16th century onwards
Bone china

For a start, see Peter Lane, Studio Porcelain (Pitman House, 1980), pp.16-17 ISBN 0-273-01538-9. There are, of course, many other sources.

Marshall46 17:06, 11 January 2007 (UTC)[reply]

Hello Marshall46, a major problem with your suggestion regarding excluding soft-paste is irrespective of individual views it that it is a recognised form of porcelainTheriac 18:15, 11 January 2007 (UTC)[reply]

Dear Marshall46, I do take your point, but I'm afraid I still agree with Theriac here. A hundred years ago soft-paste used to be called artificial porcelain by some experts, but still porcelain. Definitions are Hell and arguments about them are best avoided by lumping rather than splitting where possible, I always think. The pottery article was pretty much torn apart some time ago by a dispute about whether or not fired-clay figurines might reasonably be described as pottery and work on it has just about stopped, largely as a result of this I think. Regards, Nick. Nick 19:37, 11 January 2007 (UTC)[reply]

Material Properties

as quoted from Article (emphasis mine):

"Properties associated with porcelain include those of low permeability, high strength, hardness, glassiness, durability, whiteness, translucence, resonance, brittleness, high resistance to the passage of electricity, high resistance to thermal shock and high elasticity."

Materials are either brittle or elastic, not both. Whoever put that part of the definition in might object, or there may be a better way of describing the property that is sought after, but from a materials point of view, you need to pick one or the other.

Well now, I enjoy the melancholy distinction of having written the passage in question <g>. Actually, porcelain is both elastic and brittle, like glass for example, but I do understand that this can be confusing. People tend to think of elasticity in terms of bounciness but it's not like that. I'd like to refer you to the article on Elasticity, but this is even more of a mess than my porcelain stuff here. But please accept my assurance that brittle solids frequently are highly elastic. Regards, Nick. --Nick 22:35, 27 February 2006 (UTC)[reply]

Hi all, Yes I'd agree that a material's response to loading is complex, and can the same material can elastic and plastic properties, but perhaps suggesting porcelain is highly elastic is a little extreme. Also the property of high chemical resistance would be worth noting. Regards, Andy

Hi Andy, All, high chemical resistance is good, I'll pop it in. The question of the elasticity of porcelain is a difficult one, because of the way the term is understood in ordinary usage. I dunno, mechanical elasticity perhaps? Ugly, though. Regards, Nick. Nick 12:56, 28 February 2006 (UTC)[reply]

Nick, do you perhaps mean that the modulus of elasticity is high? -olli

Hello Olli, I've just changed the Elasticity link to Elasticity (physics). The definition given there seems to be quite a good one. Regards, Nick.

Hi Nick,

What do think of this for a definition ... not particularly snappy I know but it’s comprehensive enough, and is from authoritative sources

Porcelain - One type of vitreous ceramic whiteware. The Combined Nomenclature defines this as: completely vitrified, hard, impermeable (even before glazing), white or artificially coloured, translucent (except when of considerable thickness) and resonant. In the UK the term is defined on the basis of composition: a vitreous whiteware made from a feldspathic body (typified by the porcelain tableware made in Western Europe and containing 40-50% kaolin, 15-25% quartz and 20-30% feldspar.) In the USA the term is defined on the basis of use: a glazed or unglazed vitreous ceramic whiteware used for technical purposes, e.g. electrical porcelain, chemical porcelain etc. Note, however that the term electrical porcelain is also used in the UK. The firing of porcelain differs from that of earthenware in that the first firing is a t low temperature (900-1000oC) the body and the feldspathic glaze being subsequently matured together in a second firing at around 1350-1400oC

References

Dictionary of Ceramic. 3rd edition. The Institute of Materials. Dodd & Murfin. 1994

Combined Nomenclature, Common Customs Tariff and Integrated Tariff of the European Communities (Taric)

Regards, Andy

Hello Andy, to be honest I think the headline definition is not too bad as it is. It's designed to be inclusive and not to give the impression that there is any such thing as a standard porcelain. It drives me nuts when I see definitions like "Porcelain is made from China clay and petunse...", et cetera. Just to be insufferably picky, something completely vitrified would be a pool of glass in the bottom of the kiln; not all porcelain is translucent; tableware made in England (part of western Europe) is mainly made with porcelain containing about 50 per cent bone ash; my personal opinion is that technical and industrial porcelains don't belong in this article; not all porcelains have two firings. That being said, everything is up for discussion, of course, but most of the points in the proposed definition are already mentioned in the article as it stands. There are some truely terrible definitions of porcelain on the web, like the one at answers.com: 1. A hard, white, translucent ceramic made by firing a pure clay and then glazing it with variously colored fusible materials; china. 2. An object made of this substance. Regards, Nick. Nick 20:25, 1 March 2006 (UTC)[reply]

Tell you what Andy, forget most of what I wrote in the message immediately above. Thinking about it, indirectly you've raised some good points about problems with the definition of the term porcelain. How about this for an idea? We leave the existing headline definition much as it is, but rename the section Scope to Definitions and scope and include several definitions of the term porcelain from named sources, including the ones you mentioned, with a short discussion on the subject highlighting the differences between them. I've not seen this done before. Regards, Nick. Nick 09:09, 2 March 2006 (UTC)[reply]

Hi Nick, Thanks for the comments and in response:

I’d agree that not all porcelain is translucent nor all twice fired

I can’t agree that something to be completely vitrified would be a pool of glass. Of course this may, again ... again, be a matter of a particular definition. My understanding of vitreous is zero open porosity, i.e. completely impermeable. Certainly there are different standards depending on application, for example: BS4034 relates to hotelware and defines vitreous as exhibiting less than 0.5% water absorption when subject to a specified test procedure. However these plates were fail, and be classed as non-vitreous, by the method compulsory for electrical porcelain; basically submerge the piece in a dye solution and subject to extreme high pressure before breaking apart to check for penetration. Electrical porcelain must have zero open porosity, and hence be vitreous, yet of course its microstructure contains both glass and crystalline material

I’m not sure about excluding technical and industrial porcelains ... after all the materials and processes used across disciplines are often the same

Your suggestion of Scope to Definitions and scope with several definitions seems a good idea ... so over to you for the writing

Regards, Andy

There seems to be no discussion on the electrical properties of Porcelain. Porcelain and various other ceramics are used extensively in electronic components such as capacitors. I'd expected to see more discourse on the chemistry of the materials mentioned and their properties [dielectric constant, loss tangent, thermal coefficients, etc...]. Various ceramics are used in the electronics industry, and they carry trade names such as C0G, X5V, X7V, Y5V, etc... Some are refered to as 'Porcelain', while others are 'merely' 'Ceramics'. While most electronics engineers know the qualitative differences, it would be appreciated if someone has some physical or quantitative insight into these distinctions.

Thanks, Luko Krnan

History of Porcelain

The article fails to mention where porcelain originated. From some sources, I heard it's from China. Maybe someone can include this vital piece of information into this article. Thanks.--141.213.196.250 06:17, 22 March 2006 (UTC)[reply]

Thanks for this, quite right! Until recently the Porcelain article included quite a large section on Chinese porcelain, but this has now been moved to its own article, Chinese porcelain. The part which explained about the origin of porcelain went with it. I'll add some words to the Porcelain article to try and put this right. Regards, Nick. Nick 09:19, 22 March 2006 (UTC)[reply]

Redirect

Hello,

I added a redirect to the top of the page. Every time a search is done on "fine china" it automatically comes here. The problem with that is that one might not be searching for this fine china, but rather, this Fine China. C&R 18:24, 23 April 2006 (UTC)[reply]

Dome of The Rock

Hello Anlace, Whilst personally I greatly admire much Islamic ceramics are you sure that the Dome of the Rock is constructed, partially at least, from porcelain rather than another ceramic material? Regards, Andy

Hi All, Interesting question, Andy, I like old Islamic ceramics too but I'm not sure whether or not most of them would fall into the category of porcelain (as defined in the West, at least). The other thing that bothered me was the 100 square-metre porcelain facing units--that's the equivalent of ten by ten metres! Regards, Nick. Nick 08:20, 24 May 2006 (UTC)[reply]

regarding the Dome, all i have is the reference cited. regarding panel size, a corrected edit has been made. Anlace 19:04, 24 May 2006 (UTC)[reply]

"At the Dome of the Rock, Jerusalem, built by Caliph Abd al-Malik in 687 AD, [1] , the original marble and mosaic exterior work was replaced in Ottoman times with Turkish ceramic tiles." I have removed this sentence because the tiles at The Dome of the Rock are not porcelain. John Carswell says that it was "almost certainly" the Persian potters who had been making tiles for monuments in Istanbul who installed the tiles in Jerusalem (completed 1556). (Carswell, Iznik Pottery, British Museum Press, 1998, p.73) Porcelain was unknown in Persia and Turkey at this date and fritware, a mixture of silica, glass frit and clay was used to imitate it. Plese see the article on Iznik pottery for details of fritware. I have placed an amended version of the deleted sentence there. Marshall46 18:17, 9 January 2007 (UTC)[reply]

Hello Marshall46, I agree with all of the above, so the next step will be to delete all references to the Dome of the Rock from the article (which is, after all, supposed to be about porcelain). Those words about the tiles used at Versailles need to go too, on the same grounds. I'll do this (and take the heat as well, I suppose). Regards, Nick. Nick 19:16, 9 January 2007 (UTC)[reply]

Hello Nick. I got timed out before I could make the deletion and now I have read the reference [1] and have had second thoughts. The external site refers to porcelain on the Dome of the Rock but says nothing about the Persian tiles. Are there, perhaps, porcelain facings and Persian tiles? Can anyone familiar with the Dome of the Rock say? Marshall46 21:52, 9 January 2007 (UTC)[reply]

Hi Marshall, Kerr and Wood (Science and Civilisation in China, the volume that deals with Chinese ceramic technology) say 'Some of the earliest Islamic buildings ... such as the Dome of the Rock ... were originally embellished with mosaic and marble. This was only replaced in Ottoman times by magnificent Turkish tiles'. I am pretty confident that porcelain was not made in Turkey at this time, so on balance I think the deletion was justified. Though in fairness, K&W also say that in some respects (fineness and whiteness of the body) Iznik wares can be regarded as representing a transition from stone-paste to soft-paste porcelain. Regards, Nick. Nick 22:44, 9 January 2007 (UTC)[reply]

Tang horse picture

I'm just about to comment-out the pointer to the picture of the Tang horse that has recently appeared in the article. This is more to encourage a discussion about whether or not the picture belongs in the article, rather than anything else. My view is that the picture shows an object that probably isn't porcelain as that material would normally be recognised, either in the East or the West. But it's all a question of where the lines should be drawn. Regards, Nick. Nick 11:40, 2 June 2006 (UTC)[reply]

Merging the Porcelain tile article with this one

I'm a lumper not a splitter, but even so, there is a perfectly good tile article and I would think that porcelain tiles would be much better off there. Regards, Nick. Nick 13:11, 20 June 2006 (UTC)[reply]

=== I made two trivial edits to this article after reading the Porcelain tile article. First, I added tile to the list of uses of porcelain. Next, I changed "ideal insulator" to "excellent insulator." "Ideal" is a technical term in physics. Diamond is closer to the "ideal" than is porcelian. Arch dude

Suggested for deletion

Hello all, I think the following should be removed by discussing stoneware and not porcelain it just complicates the article... any thoughts? Some clays used for making ceramic wares are too cohesive to be thrown on the wheel. Examples include the brown clays used to form the bodies of the red stonewares of Yixing in the Chinese province of Jiangsu. As a result the Yixing-wares are almost always hand-built. Regards, Andy

Hello Andy, yes, I think you're right, blow it away. If I remember rightly, it's a hangover from the days before Chinese porcelain was hacked out of the main article on porcelain. Regards, Nick. Nick 08:09, 13 July 2006 (UTC)[reply]

Hi guys. Yes, probably doesn't belong here. But how 'bout moving it or something like it to Yixing clay? Yes, another clay article with a clean up tag. Best to you both. WBardwin 08:49, 13 July 2006 (UTC)[reply]

Hello to you both, Thanks for the response. I've deleted the section and transfered it, with a little editting, to Yixing clay as recommended by WBardwin Regards, Andy

Material Properties

There seems to be no discussion on the electrical properties of Porcelain. Porcelain and various other ceramics are used extensively in electronic components such as capacitors. I'd expected to see more discourse on the chemistry of the materials mentioned and their properties [dielectric constant, loss tangent, thermal coefficients, etc...]. Various ceramics are used in the electronics industry, and they carry trade names such as C0G, X5V, X7V, Y5V, etc... Some are refered to as 'Porcelain', while others are 'merely' 'Ceramics'. While most electronics engineers know the qualitative differences, it would be appreciated if someone has some physical or quantitative insight into these distinctions.

Thanks, Luko Krnan

Hello Luko,

You are correct that both porcelain and other ceramics are used in electronic applications; it is also worth noting a related use of porcelain, which is for high tension electrical insulators. I guess you are aware that porcelains are types of ceramic, and the latter is a very broad and diverse group of materials. Regarding trade names such as C0G& X5V it is probably worth checking wikipedia’s policy on commercial references, and I personally think a better article would result from referencing the material & applications, say BaTiO3 PTC, rather than companies’ products. I would agree that detail on chemistry and properties should be included, however as wikipedia is only as good and comprehensive as its contributions why not start yourself! It may well stimulate others to join in

Oh, I repositioned you post into a more chronological order of the tak pages ... hope that's OK

Regards,

Andy

Hessian crucibles

Hello All, It seems that Hessian crucibles, much favoured by alchemists from the middle-ages onwards, contain mullite. Very interesting, a ceramic with a body made using china clay, fired at 1100 to 1200-deg C, containing mullite, a couple of hundred years before Meissen. Would it be reasonable to describe this as porcelain? See:

http://www.ucl.ac.uk/archaeology/staff/profiles/martinon/Martinon-Torres%20et%20al%202006%20Nature.pdf

Really just for interest, not to start a war. Regards, Nick. Nick 17:42, 6 January 2007 (UTC)[reply]

No it is not porcelain. Interesting as the article is as a quick read I personally find nothing particularly surprising in it, and the bit about "Mullite (Al6Si2O13) has been developed for a wide range of applications in modern ceramics, including for building and optical materials, and for thermal-protection systems and in liners for aircraft engines." is a little misleading as it builds the "discovery" up to be more significant than it actually is; consider an alternative to reference it to traditional porcelain, where depending or composition / firing mullite would also be found, but would not sound quite impressiveTheriac 19:54, 9 January 2007 (UTC)[reply]

Editing?

Would the article suffer at all if the following was removed as I can't it brings anything to a reader: "Porcelain has many uses but this article is concerned mainly with its employment as a material used to make objects of craft and fine art, including decorative and utilitarian household wares. This follows the Wikipedia policy of drawing a line between technology and the arts, though in the case of porcelain the line is a difficult one to draw. Industrial and other uses are not covered here."ThaxTheriac 19:35, 9 January 2007 (UTC)[reply]

Fine by me... what does anyone else think? Teapotgeorge 19:52, 9 January 2007 (UTC)[reply]

The new edit is an improvement but how is "used to make objects of craft and fine art, including decorative and utilitarian household wares." actually helping? Removing it would not damage the article, and it would avoid the debate currently ranging over at ceramics (art) about what is to be classed a a ceramic art objectTheriac 20:02, 9 January 2007 (UTC)[reply]

Well now, the words in question were written by me in an attempt to to limit the scope of the porcelain article to the arts and crafts. I'm not particularly concerned about my deathless prose being extinguished, but it would open up the article to all of the uses of porcelain. Is this really what is wanted? What is wanted is a lot more words in the article, it's in a sad state at the moment. Regards, Nick. Nick 20:13, 9 January 2007 (UTC)[reply]

Hi Nick, I meant no criticism of your words. I see nothing wrong with extending the use of the article, after all a reader visiting Wikipedia to learn about porcelain should be given this information. Also the early part of the article already mentions non-art use, such as false teeth and crowns (and as these are so highly specialised and have very distinct formulations, including no clay, as to perhaps justifying being away from here is another argument) Hope you don't mind that I've repositioned your last comment so that it is chronologicalTheriac 20:40, 9 January 2007 (UTC)[reply]

I've been tidying the "see also" links can anyone see any reason for keeping "Lenox" as a link? Teapotgeorge 20:33, 9 January 2007 (UTC)[reply]

Hi Teapotgeorge, The internal link? If so whilst it's not the best of articles by far but why remove it? It may improve with time. I can see a reason though to delete an external link, www.highendcollectibles.com, as it is commercialTheriac 20:44, 9 January 2007 (UTC)[reply]

Yes you are right ... I just thought it added nothing much to the Porcelain article at the moment. www.highendcollectibles.com should go I agree. Teapotgeorge 20:53, 9 January 2007 (UTC)[reply]

Hi Teapotgeorge, just deleted the commercial link, thanxTheriac 20:56, 9 January 2007 (UTC)[reply]

Translucence quality : need photo

One of the unique quality of porcelain is the translucence quality. Anyone to contribute photo to show translucencity ? --Sltan 13:00, 19 January 2007 (UTC)[reply]

Hi Sltan. You are right that translucency is a prized characteristics for many porcelains (but not all). It would be good for a photograph to illustrate this to be included. I have some but these are not open copyright. Maybe others can help. ThanxTheriac 13:05, 19 January 2007 (UTC)[reply]

KT&K

The following sentence is (1) POV, and (2) unsupported by any citation or reference. Ca anyone help? ThanxTheriac 15:03, 10 February 2007 (UTC) "Heinrich Schmidt, a designer from the Meissen factory, went on to establish his reputation in America when he joined the Knowles, Taylor & Knowles factory in East Liverpool, Ohio in the 1890s. Schmidt was the creative force behind KT&K's famed Lotus Ware, commonly acknowledged to be the finest porcelain ever produced in the United States."[reply]

Porcelain of Capodimonte

The recent addition needs quite a bit of attention, including supporting citations, and explanation, or more likely another choise of words, as to what is meant by "forging" of porcelain ThanxTheriac 13:36, 11 February 2007 (UTC)[reply]

thank you theriac I try to expail better. Anyway it's a way of working by hand the porcelain when it is not yet cooked. I'm italian and I don't know the correct term in english. If you understand what I mean please correct me. —The preceding unsigned comment was added by 213.230.129.21 (talk) 14:11, 11 February 2007 (UTC).[reply]

Hi 213.230.129.21. Thanks for the reply, and welcome to Wikipedia. I do not think any difficulties you have with English would be a problem as they are many editors who could assist. But it is imporant that entries are supported by references and citations from books and journal articles. That you recently added on "Capodimonte porcelain" had no supporting citations, and to remian it needs some. Also it may be better to create a new article for "Capodimonte porcelain" rather than including it in the porcelain article. An internal link from "porcelain" to "Capodimonte porcelain" could then be included. ThanxTheriac 09:14, 12 February 2007 (UTC)[reply]

Thank you again Theriac, I've found in wikipedia the history of the museum of Capodimonte that is very famous in Italy, above all among the experts of History of Art, like me, I create links with the Museum and I try to do the external link.Thanks