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Porcelain Survey


glazenerd

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Being recently, almost, semi retired: I need a summer project. So I have decided to work on some porcelain clay bodies to occupy my time and waste my money on. With that, I have a few questions for those who use porcelain:

 

1. What are the properties that you dislike the most.

2. What properties do you find most beneficial.

3. How important is translucency or whiteness?

4. Would you make larger pieces if the clay had the mechanical strength?

5. What cone do you fire to the most?

6. What properties do you wish porcelain had?

7. Do you throw, press, hand build, etc?

 

Answer any or all, or just ramble or rant: your call. Just curious to see the general response. Will give me some ideas about what issues to address. Thank you for your time.

 

Nerd

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1. Low COE. I don't like reworking a lot of my glazes for these clays. If I had started in porcelain it wouldn't be an issue though. Or if I didn't mind crazed pots, but I do, unless I am trying to achieve that look. /ramble

2. Plasticness. 

3. Whiteness is important if I am using a clear, or if I am leaving some of the clay showing for aesthetic purposes. Otherwise it isn't. Translucency means nothing to me I am not making lamps.

4. The only problem I ever had with porcelain was that I like to make large bowls with large beautiful curves and a small foot. These usually slumped. I also put birds figures on some of my rims, and these warped the rim. This doesn't happen with my stoneware.

5. ^6

6. i think it has all the best properties. I would use it except I like the look of stoneware when my glazes are thin, the brown comes through, and that is why I use it instead of porcelain. (edited for clarity. thanks oldlady).

7. throw only atm.

 

Good luck with the body. My favorite porcelain was probably frost.

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Being recently, almost, semi retired: I need a summer project. So I have decided to work on some porcelain clay bodies to occupy my time and waste my money on. With that, I have a few questions for those who use porcelain:

 

1. What are the properties that you dislike the most.

that it sticks to shelves (plucking) and lids

It weighs no much -it would be better is it was more like popcorn so as I got older my 10 tons a year was less hassle to move.

It would be nice if people just paid me direct for the clay without all the trouble of moving Throwing firing pricing driving selling-just make it so they buy the clay in a box-much easier on the body-so make it brain wash them into thinking its easy to work with?maybe a scent on the box?

2. What properties do you find most beneficial.

The color of the glazes on it-it pops color wise,the hardness ,toughness, strength, feel, look

the drying capabilities -the softness of raw material-the pureness. It really helps with production as it dries so fast and even.

Great in salt fire with colorants on it.

I like it because It sells itself with bright glazes on it-no talk needed

3. How important is translucency or whiteness?

whiteness yes translucency no-only if I made pots that called for that and I do not.

4. Would you make larger pieces if the clay had the mechanical strength?

I can throw a 20 # bowl never wanted a larger one-seems fine strength wise?

so thats a NO

5. What cone do you fire to the most?

soft cone 11 almost always Some special kiln loads at a soft under cone 10 fire for the glazes

Gas reduction fired.

6. What properties do you wish porcelain had?

This is to general a question?- It's not as forgiving as stoneware by a long shot.I like Daves porcelain for throwing as it throws so well but is a bit grey-I like Babu's whiteness but it throws like cream cheese. Porcelain never slacks well or reclaims well once it dries-it looses it legs. Not an issue really as I just let it go at that point to become road fill.

I like the 550 from Laguna for its color but it throws less than Daves but more like Babu, Some of the finer porcelains glassify so they seem over vitrified and seem weaker or say more brittle.

I use 1/2 and 1/2 and add more Daves to dilute the 1/2 thats not porcelain for slab work-also my special Daves with white fine grog for slab work

7. Do you throw, press, hand build, etc?

I use 1/2 and 1/2 and add more Daves to dilute the 1/2 thats not porcelain -for slab work-also my special Daves with white fine grog for slab work 

Most of work is thrown from straight Daves Porcelain

 

8. How much have you spent on Porcelains

a small fortune spread out over 40 years.

 

9.Why did Apple make the apple white like porcelain ?

mass appeal to porcelain makes for better sales

 

10.Is your Christmas going to be a white Christmas or is it to early to think about that season?

Bingo

 

11. Why do they call it the white road (after porcelain) when roads all get dirty and are not white?

only Dirt Roads on this board has the answer

 

 

Answer any or all, or just ramble or rant: your call. Just curious to see the general response. Will give me some ideas about what issues to address. Thank you for your time.

 

Nerd

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joseph, does your sentence mean "why i use it instead of porcelain?"  or you apply a coating of stoneware on top of porcelain?  

 

i have some frost and want to use it but i read here that it does not like very many glazes.  going to try marcia's celadon recipe when i make something in frost.  you use commercial glazes, don't you?

 

I edited the post for clarity. I always forget to use words better when things actually go over things in ceramics instead of using the word over as in my choice over. 

 

That was my problem with porcelain, you need to find low expansion glazes to go with it if you want them to fit right. I just didn't feel like doing it and I dont really like making super colorful pots, so those 2 things is why I didn't keep working with porcelain. I actually enjoyed the challenge of the body and once I started getting it, i liked throwing with it a lot. 

 

oldlady, I am not sure if your asking me if I use commercial glazes? I started with commercial glazes but I haven't used any in a long long time, too expensive to experiment with and I love experimenting.

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The  "tackiness" comes from extra fine particle sizes in the kaolin. If you would forego translucency and a touch of whiteness for strength: that could be done. Again though: the pottery business buys less than 3% of annual production of most all products we use. Read an article the other day that stated we only buy 0.10% of all clay produced. The clays sold to the paint, plastic, and rubber industry is a much better grade, than what is sold to us.The particle sizes in most of the pottery books given for clay are wrong: they date back to the Wendt scale of 1922. Kaolinites were researched at a University in NC  in 1959, and almost all were found to be off by as much as 300%.

Probably the most interesting study I read came out of the University in Little Rock (I think; read too many) Kaolinite clay beds were [primarily formed when glaciers came through. Most beds are organized in deposits from north to south; that makes sense. The northern end of the bed has the heaviest grains, and the highest amounts of impurities such as iron, manganese, and others. The southern end of the beds are almost pure kaolin, with the least impurities and the finest particle size. Want to make a guess which end of the bed is sold to the pottery industry?

The long held standard for porcelain as been 1/4th part blending: 25% kaolin, 25% ball clay, 25% silica, and 25% feldspar. Then it moved to tri-blending: more kaolin with two different ball clays, or vice versa. Less silica, or more feldspars: various combinations of the basics. Then a (CP) theory, closed packed: various grain sizes to fill all the microscopic voids. All of these parameters are still from the 50,60's: with the only modern twist of air-floated materials.

Interesting though is that commercial applications are blending as many as five different clays, several silicas, and a host of modifiers to control drying, warping, and strength. Even more interesting, clay producers have to provide them with clays to their specifications: we get the leftovers. I do not buy my zinc, silica, Nep SY, and a few other products from standard pottery suppliers: because the quality is so poor. Perhaps it is time to do the same thing with clays.

 

Nerd

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1. What are the properties that you dislike the most. Porcelain should never have ball clay in it. It ruins the feel of the clay. White stoneware is not an acceptable substitute for porcelain. They are two completely different animals.

 

2. What properties do you find most beneficial. Porcelain by its nature is smooth, which is probably the most attractive quality for most people. But its lack of plasticity (compared to stoneware clays) is what I love about it. Nothing else feels like it. There is a rubberiness to it that makes it unique.

 

3. How important is translucency or whiteness? Whiteness is important, but translucency is not. Most people who work in porcelain do not work thin enough for translucency to come into play. As translucency increases, so does warping. I would rather have stability.

 

4. Would you make larger pieces if the clay had the mechanical strength? You bet. I have made many 50 pound planters with porcelain, specifically Standard 365 cone 6 porcelain. No warping or cracking.

 

5. What cone do you fire to the most? cone 6, although I worked in cone 10 for many years.

 

6. What properties do you wish porcelain had? See above.

 

7. Do you throw, press, hand build, etc? Throw.

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For me it's all about porcelain. I use Babu for the whiteness. I use clear glazes or translucent so and the whiteness makes the glazes much brighter. I have used stoneware and even other, less white porcelains, but when I'm doing black and white, the white needs to be as white as I can make it. Even so, clear glazes leave a greenish tinge that I've had to live with.

I love throwing cream cheese.

I can throw porcelain as thin as I need it. I'm not going for translucent, just a nice lightweight mug or bowl.

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@glazenerd do you have a link or search suggestions for the technical papers you are talking about? I have only thrown a few pieces with porcelain, and my favorite thing is how soft it is on my hands. Warping, slumping, and cracking are due to lack of experience for me. I am intrigued by Bryan Hopkins low fire body. I am planning on testing and ultimately developing a recipe with similar characteristics. I have read a lot about materials on Digitalfire and I attended his talk at NCECA, but any new information is helpful. Is this the paper you are talking about?

 

http://dergiler.ankara.edu.tr/dergiler/31/1386/15749.pdf

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Tri:

I have a tendency to read techinical papers from/about the plastic, paint, rubber, and technology industries. They use kaolins, ball clays, and a host of other minerals as we do. Reading info from the commercial ceramic industry is also helpful. They tend to look at clays etc from a chemistry/engineering aspect which gives some insights into "new" perspectives. I work mainly with crystalline glaze: which is zinc silicate. Oddly enough every circuit board is covered with zinc silicate: and I adapted some of their concepts in processing. So now I am looking at clays through their eyes: instead of the standard pottery views.

http://www4.ncsu.edu/~hubbe/CLAY.htm

This is a very short article, but it gives you an idea. Some are 20-30 pages long and would bore most to tears.

or doi:10.1016/j.progsolidstchem.2005.05.001 - 8148thermodynamic_correlations_and_band_gap_calculations_in_metal_oxides.pdf

Nerd

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Chris:

I have been formulating porcelain primarily for tile work, but inadvertently came up with a blend that acts more like modeling clay. I went through your gallery to see the details of the pieces you make. I know you use Frost; but can I ask about the properties you find appealing about it?

 

After playing with it for a bit, I decided to do a torture test. I made a 2" wide ribbon and wrapped it around a 2" PVC pipe to make an arc. Cut some down to what amounts to shredded carrot looking slivers. Curious to see how this "mistake" acts when fired. The normal tackiness of porcelain clay until you brush/sponge water on it: then it gets rather sticky. It has a higher Si/AL ratio the standard cone 6 porcelain, so it should have better mechanical strength.

 

Nerd

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Lets see if my master plan works? I have formulated a high alumina kiln shelf body with a COE of 6.82. Working on two porcelain formulas: one for tile and one for throwing with a COE of 7.24. All in order to fire my crystalline glaze with a COE of 7.31. (Glazemaster #'s.) The number one problem with crystalline glaze is crazing and clay/glaze interface checking due to disproportionate COE's. I cannot change the recipe of the glaze, or add the usual fixes for COE issues because it hinders crystal development: so that only left me with fixing the clay and shelves. Think from this point forward, will formulate the clay to match the glaze.

Rather interesting to go through kaolin bodies sold to the paint, plastic, and rubber industries: but not available to us. Customized blends of particle size, iron, sodium, and titanium levels for specific uses.

Nerd

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Chris:

I have been formulating porcelain primarily for tile work, but inadvertently came up with a blend that acts more like modeling clay. I went through your gallery to see the details of the pieces you make. I know you use Frost; but can I ask about the properties you find appealing about it?

 

 

Nerd

I use Frost as my teaching clay body because it shows the colors really well when it is wet and manages quick drying.

I use it in my own work when translucence is not primary ... It is fairly forgiving and does not need a lot of babying.

 

BUT ... Southern Ice is still my go to porcelain when I am making what I would call 'signature work'. Yes, it is a very frustrating clay to work with but the results are simply gorgeous. The white is beautifully translucent and the colors are alive and vibrant.

 

I am missing it now because the body I am working with is a 'dead' clay ... dull colors but easy to throw for my color experiments.

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I really dislike throwing with porcelain. Any time I try it feels really weird, like it has this outer skin and very non-Newtonian. Like throwing with a glaze more than clay.

 

I love the strength and look when fired but hate working with the stuff, it is very unforgiving and hard to fit into my working style. Maybe I haven't given it enough of a shot. I do have plans to start casting porcelain from moulds and that is probably the best way to fit it into my work.

 

If you can make porcelain feel like stoneware that would be great  :D but probably impossible because I see it more a glaze than clay in its definition.

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1. What are the properties that you dislike the most.I like the smoothness while throwing and the forms achieve

as well as the memory of surfaces.

d.the price

 

 

2. What properties do you find most beneficial.

the forms I can achieve

 

3. How important is translucency or whiteness? When I fire to the maturity of the clay it is important. When I fire Alternative Firings, the smooth surfaced after burnishing is important.

 

4. Would you make larger pieces if the clay had the mechanical strength? The strength failed during a recent wood firing to ^10+ and stacked on side. Normal positions are fine. I sometimes torch the clay while forming to give it strength.

 

5. What cone do you fire to the most?

06, 6, and on occasion 10

 

6. What properties do you wish porcelain had? self forming at my command

 

7. Do you throw, press, hand build, etc?

throw, press, slump, handbuild.

 

I love Coleman Porcelain. Just got some Nara or Nora porcelain. So far I like it.

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post-1954-0-82622800-1459431221_thumb.jpg

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Marcia & Joel

 

Had the chance to talk to a West Coast clay exec outside of the hotel in KC. The usual Nerd conversation about the technical aspects of porcelain and particle sizes,etc. One of their most popular brands of porcelain is very close to the old standard of 1/4 kaolin, 1/4 ball clay, 1/4 silica, and 1/4 feldspar. Which also lead to a conversation about material purity and industry standards.

Which leads me to an answer to both you and Joel: there are a host of kaolins and ball clays that are not available to the pottery industry. The most interesting, are the ones with large particle size: larger than what we use. In addition, iron and sodium contents under 0.10%: which affect color and property. Sodium might be fine for glazes, but it is a lousy flux for porcelain. So I do believe there are ways to increase mechanical properties, and still achieve high whiteness. The high cost porcelains usually have NZ kaolin or grolleg.

The goal at this point anyway: so its back to test, test, test, test, test.... had to add a few tests because it will take some time to figure out the puzzle. I think the key will be to forsake industry available clays, and look at specialty industrial use clays.

 

Nerd

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Marcia :)

 

All I know (well not all), but Custer is out the door. Might be the old stand by flux, but way too unpredictable in quality control. G200 is probably right behind it, it is just ground feldspar. G-200HP perhaps, processed to maintain a designated K20 level. Using my PH meter to build a data base of alkali levels, instead of solely relying on flux %'s. Same method of formulation I developed for crystalline glaze: maintaining a narrow PH range per glaze batch. It should equate out to alkali range X for cone 6, range Y for cone 8, and range Z for cone 10. Currently porcelains run from the 5.2 to 6.0 range in COE, have been formulating in the 6.5 to 7.2 range, which should solve a host of crazing problems. I have a couple of test bars that look like milk glass even though they are nearly 3/8" thick. So I am doing what I love the most-experimenting. So far I have been running 12.0 to 13.5 shrinkage, which for porcelain is great.---then I will deal with LOI and other issues.

Nerd

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1. What are the properties that you dislike the most.

    getting glazes to fit,  it's workability is very sensitive to consistency too wet or to dry, thixotropic......

2. What properties do you find most beneficial.

     i find that porcelain will obeys my will better than other clays

3. How important is translucency or whiteness?

     i like white clay but not that important  usually the whiter the more expensive

4. Would you make larger pieces if the clay had the mechanical strength?

    didnt know it didnt have mechanical strength..... but i haven't built anything huge

5. What cone do you fire to the most?

    6 ox but i wish i could fire more 10 and even more woodfire

6. What properties do you wish porcelain had?

 

7. Do you throw, press, hand build, etc?

     yes

 

i make my own cone 6 and 10, +  woodfire clay EPK based,  its local (ish) source.   both porcelainish  depending on how strict you are with definition

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Guest JBaymore

Wow...... did you buy a dilatometer?

 

best,

 

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

 

 Currently porcelains run from the 5.2 to 6.0 range in COE, have been formulating in the 6.5 to 7.2 range, which should solve a host of crazing problems. I have a couple of test bars that look like milk glass even though they are nearly 3/8" thick.

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