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Dave K

Tips On Using Porcelain

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I have been throwing for about two years now and would like to try porcelain. I am considering one of Standard's cone 6 porcelains. Any tips or suggestions for a clay and how it will differ from stoneware? I have heard it can be difficult to use but I would like to give it a try.

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I haven't tried Standard's porcelain. I have tried many types of porcelain over several decades. 

Porcelain absorbs water faster so don't throw slowly. Get it formed without a lot of water. It warps easier, and can crack easier. Best to handle it as little as possible after thrown.

Some porcelain can flux out a glaze more than stoneware, so test your porcelain before a glaze firing.

 

Marcia

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One thing that shocked me about porcelain is how fragile it is before bisque.  I like to do a lot of sanding etc before I bisque and I had to totally relearn how/where to handle it during that process.

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Dave,

 

If the cone 04 has worked ok for you with  cone 5-6 stoneware it should work ok for porcelain cone 5-6 porcelain.  Try it and see what happens. 

 

My experience with porcelain is that requires a more subtle throwing technique than regular stoneware.  I see porcelain being more elastic than stoneware clay bodies. 

 

Throwing bowls is an example. 

With stoneware, the bowl generally stays round while opening and shaping the bowl.  A porcelain bowl become oval while opening but will spring back to a round form when you release it with the wheel still spinning.  Of course the dimension you have reached away from center is smaller than when you released it.  The edge of the bowl is more like a rubber band than a metal hoop.  I also allow three or more rotations of the wheel before I release my hands when throwing porcelain and always release with the wheel turning for several seconds before stopping the wheel. 

 

If you become impatient and use the brute force techniques that worked OK on stoneware, you will likely not like the results with porcelain.  

 

Just practice and pay attention to what is happening and practice. 

 

My initial try proved that throwing thin was not a way to wind.  But with practice it became easy to achieve thin if I got it to almost thin enough, stopped, relaxed, let the clay firm a bit, and returned to expanding or pulling up.

 

 

LT

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You guys are scaring me a little. 365 lists the bisque fire at cone 06. Most everything I do is at 04. Is the 06 critical?

 

I bisque it at 04. Porcelain is a little more porous than stoneware when bisqued, so at 04 it's a little tighter and will give you more control in glaze application.

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If you're still looking for recommendations, I've used Standard 551 for a couple years now and I think it's great. I've done a lot of stuff to it (hydroabrasion, handbuilding, altering) and never had any of the cracking or warping problems that normally come with porcelain.

 

The only drawbacks I've heard of or experienced is that it's not as translucent as other porcelain. Also, if you make use of a lot of unglazed surface, some people don't find it as attractive as other porcelains might be.

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I use Standard 213 porcelain, decorate with underglazes before bisque (^04), and finish with a clear glaze (^5-6). The unpainted porcelain is creamy colored rather than white. I throw my bowls about 1/4" thick or a little thinner, and I do not use a lot of water when I throw. I don't have problems with the clay deforming.

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Sometimes with thinner porcelain its easier to fire it as is in low bisque fire and then clean it up by sanding and scraping. Its very crumbly in the green stage.

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I mistakenly put a cone 05 glaze on several cone 6 green porcelain pieces. They are not meant to hold water so if I just go to 05 I guess I'll at least see what the glaze looks like. But I really want to fire to 6. Is the low fire glaze likely to just burn and turn brown???  Would it make a difference if I did it in 2 fires (05 and then 6) , instead of the single fire straight to 6 that I have been doing? 

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My biggest issue with porcelain (Standard 257) is that it dries very quickly and unevenly. In my experience, if you are not careful, a lip might become bone dry before the foot is ready for trimming.

 

Arelated problem is adding attachments. With mugs for example I find that by the time the bottoms are ready for trimming, the walls are often too dry to for the handles.

 

you can add a little vinegar to your throwing water to help with fast-absorbing "thinner" water and not get soft and slushy too fast.

 

Marcia

thats a great tip

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You need to dry/store your pots in a damp box or similar humidity controlled environment so that

 

A) every part of the pot loses water at the same rate, and

 

B) at any given moment the moisture content of the clay in any part of the pot is the same as everywhere else.

 

This includes your handles which you plan to join to the mugs - keep them in the same damp box you keep the mug in. Over a day or three their moisture content will equalise.

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I am reading what you all are saying about porcelain and it makes me smile a little. All these things you mentioned here were things that I believed the first 25 years of working and teaching ceramics. In the very early stages of my career, I had my porcelain slumping and sticking etc. Those years everyone said you have to be experienced to work with porcelain, so I waited some years and tried it again. I made some high fire bowls and were very proud of myself that I could make a simple bowl in porcelain. 

Then I switched to pit firing porcelain. I worked with it in the pit for about 10 years in South Africa and the USA, making bowls and sculptural pieces as big as 18 - 24 inches. One day I wanted to get back to high fire porcelain. I ended up with pieces breaking, tearing and getting all over the place. It took me back to the basics of clay and what I discovered there, was that I could have worked with porcelain from the very first day of my career, I someone explained to me the character of porcelain.

 

Since then I did porcelain workshops across the world and wrote several articles about it. On my blog is several articles for anyone to read and there are several in other places available on the internet ( including YouTube), so if you are interested to learn more, you will find the info there. 

 

In the meantime I can tell you that porcelain is a diva that demands respect and force you to follow the basic rules of ceramics and by the way, I do not throw porcelain fast. I take as much time as I need to throw very thin pieces and then I alter them at the leather hard phase. Hard to believe , but true. 

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I have been following this thread without comment until now. All the problems usually associated with porcelain bodies.

All the issues listed can/could be addressed, but usually are not because of pricing points. Keep talking, I am listening intently.

 

Nerd

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one thing i have not seen anyone mention is that porcelain does not have the craggy, groggy feeling that some people find in stoneware.  it was once described as "putty" by a fellow potter who had trouble adjusting to it.  and it helps when throwing anything to keep the fingers following all the way up, sudden movements are bad in any kind of throwing and porcelain is less forgiving.

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Like Nerd, I've been following this avidly. Not because I can add advice, but because I've just done my first work with porcelain.

 

I don't do any throwing - it's all handbuilding - but some of the advice is still helpful. Such as working quickly; I saw for myself how quickly it dries. Interestingly, of my first four pieces (all experimental - what else could they be) one split and fell apart while it was drying. It was made of five pieces and every single one of them tore significantly. And most of the joins failed as well. It was so thorough in its collapse I have to laugh and say I learnt a lot from that one!

 

The others worked well, although I expected those to split as well. So there seems to be more unpredictable behaviour from it than from stoneware. That's OK, it goes with the reputation. Smoothing with a sponge is a great tip.

 

Thanks from me as well for all this advice!

 

Girts

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After working full time in porcelain for 35 years I will add that you will have to just learn how it dries and what glazes do on it. It does dry different than stonewares and glazes do flux more and it can crack and warp more but it's got a spectacular look to it and glazes pop on it.i mostly throw but do hand build teapots lids and make flat slab forms. It's like most things in ceramics you just need to work a lot with it to learn what it does.

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Hi, I'm new to porcelain and loving carving into it. I hand build small pieces and carve reliefs. I winged my first firing and ramped it full to 2000F (I found instruction online saying that it should be cone 6 but my electric kiln only goes up to 2000), and only held it for 1 minute because I couldn't find anything about ramping. I received the porcelain from a friend, it's Dove. Does anyone know what the ramping schedule should be??

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Weberart, There is many opinions about the temperature at which porcelain must be fired. It sounds like the small pieces you've made are just for fun and not functional. In such a case it is okay to under fire it, unless people may confuse it for something functional that must hold liquid.

 

It is a pity that your kiln cannot fire higher, because at 2000F (1093C) the porcelain clay may still be porous ( depending on the fluxes in the clay). It may work well in a raku or other alternative firing though. 

 

Mark, I fully agree with you about the drying. Not only that: if potters understand  the different drying stages, they will also be able to eliminate some cracking and warping.  

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Thought I'd jump in on this thread. I'm curious how other's prepare porcelain for throwing?

 

I've been using Audrey Blackman for a few months now (after throwing with stoneware for a couple of years) and out the bag its very soft and flexible. If I wedge on a wooden table it doesn't firm up much, and if I wedge on a plaster bat it starts to crack or get short after a few pushes.

 

I had a bit of a revelation today, I was throwing with Earthstone Glacier for the first time and it was a similar consistency as the AB out the bag and if wedged on a plaster bat was splitting etc. After having a couple of bowls collapse I put the resulting sloppy mess on a plaster bat and came back to it after about 10-15 mins. I wedged it up and it was firm without cracking/splitting, I then threw with it and managed to pull some nice delicate walls that didn't collapse.

 

No one else really throws with porcelain at the studio I go to so asking questions like how firm it should be and how to prepare it properly is difficult.

 

So, how do you know your porcelain is 'ready' for throwing?

 

Any help is much appreciated.

Martin

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Martin, I have brought a small piece of Audrey Blackman porcelain with me back from my workshop tour through Europe this past summer. While I was there, I made one of my large signature bowls on the wheel with Audrey Blackman. I found it the best of all the clay bodies that I used while in Europe. Next to that was Ming porcelain. I also worked with Southern Ice ( which is what I am using in my studio here in the USA), but did not like it at all. It had to do with the "ripeness" of the clay and not with the dryness.

 

So my first piece of advice to you is to check how long ago the clay was made. When it splits it is either too dry, or you pressed too hard, or the clay is too fresh. 

 

 As far as how dry the clay should be when you start throwing it, I have the following advice: 

 

Never start throwing straight from a bag without first wedging the clay and then allow it to rest over night , or at least a few hours. You want the clay to spread its moisture evenly throughout the clay. 

 

Porcelain must move smoothly on the wheel with just a light touch, because it is short in nature. When you center it, you do not need any force; If you have to use force, the clay is probably too hard. On the other hand if the clay spreads out out of control when you center it, you'll know the clay is too soft. 

There is a YouTube video where I center porcelain, it should give you an idea of what I am talking about.  

 

Antoinette Badenhorst

www.porcelainbyAntoinette.com

http://teachinart.com/index.html

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