Persnickety Porcelain: How to Minimize Your Loss Rate With this Gorgeous, Yet Difficult, Material

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Porcelain is a clay body that draws in many a potter because of its bright white color, translucency, and the way glazes look oh so fabulous on it. But it’s a fussy little clay body susceptible to collapsing during the forming process and warping during the firing.

But it’s so pretty and I, for one, still like to take my chances with it. With practice, you can learn learn how to work with this persnickity clay and minimize your loss rate. Today, Gwendolyn Yoppolo explains what porcelain will put up with from the wet phase to the bone-dry phase. – Jennifer Harnetty, editor.


Minimizing the Lost Rate

by Gwendolyn Yoppolo

Porcelain commands us to be attentive in our touch and responsive to its needs. Beyond the basic technical demands that clay bodies all have in common, porcelain also needs to be treated properly to avoid warping and cracking during drying and firing.

One of the most important things to remember is to watch your timing-this is best learned through experience.


Pure white and wonderfully delicate, porcelain is a gorgeous and notoriously challenging clay body. In Masters: Porcelain, you’ll see the incredible work of 40 artists who have mastered the material. Curated by Richard Burkett, this collection expands and challenges traditional perceptions of what the medium can — and should — do.

If you are hooked on porcelain, Masters: Porcelain is the book you need on your coffee table!

Learn more…


Building onto a form that’s too soft causes slumping. Adding softer clay onto a form that is too dry results in cracking. Altering and/or bending a form that’s too dry or leather hard causes warpage and cracking.

In general, join only pieces of similar dryness and reinforce all joints with extra clay and compress them together with a rib.

Slow and even drying is critical. Periods of rest, where the pieces are wrapped in an airtight chamber to slow drying and redistribute moisture, do help. The clay has a chance to get used to its new form at each phase, without having one part dry too quickly for the rest of the piece.

Another valuable technique is to restrict movement of the piece during the drying phase.

Here is a loose guideline and timeline for when to do what while working with porcelain. The phases are not distinct, but are separated out from the continuum of the entire process for the purposes of discussion. In fact, they blend together in many ways, especially the “cheese” sections. Because porcelain is thixotropic, it has a nice way of resoftening once it has reached the hard cheese stage, so you can actually go back and perform some soft cheese processes. Porcelain also rehydrates locally to some extent, so you can go back in a concentrated area. These guidelines are designed as a starting point for you to figure out your own way to achieve success.

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**First published in July 2014
Comments
  • I love working with porcelain, but the cracking during drying and bisque fire have been discouraging. The tips in this article make a lot of sense. I’m anxious to give porcelain another try. Thanks to Gwendolyn for a great article.

  • There’s something about Southern Ice porcelain. Its finicky nature…i just have to keep working with. It’s as if it’s a hardheaded lover lol. Its translucency is so worth the heartache.

  • As a professional potter, I have found a few clay bodies I really like and stick with them. If porcelain is what you like, I would say go ahead! But do nothing but porcilain. Make it your best friend. Then you will learn all the nuances of it, and will be able to get great results from it. I just don’t feel I have the time to add another aspect in working with it; There is still so much to explore with the clays I use now.

  • I love working with porcelain because of it’s bright white colour and potential to be so smooooth. But I’m in a community kiln so you never know what your work will turn out to be and just yesterday I had a platter crack in the middle after firing. But I won’t turn my back on porcelain, it’s too nice and white and bright and smoooooth….
    Caroline

  • I SO love porcelain, and use it without any trouble at all. Maybe its because I do just handbuilding, and work fairly small (but not always…), I don’t know, but I almost never get cracks or warpage. I use mostly Georgie’s Silver Falls Cone 6, beautiful and translucent. However, I also love the rich reds and wonderful “tooth” of terra cotta and would never limit myself to just one type of clay. Try porcelain, you will love it! My question about the above article is…what is meant my “Processes Supported” ? It is listed under every phase but never explained what is meant by that.

  • Always fire on porcelain cookies.. Paper-clay helps with the hand built bits. You can add almost dry to almost dry with a dab of slip.

  • Not sure what a porcelain cookie is….something like the wads used in salt firings? Also not sure what ‘processes supported’ means. My problem is that my very thin, large porcelain bowls warp and fire out of round. I use a cone 6-8 porcelain and only fire to cone 6. Very frustrating so any help would be welcome as Yoppolo did not discuss this aspect. Ann E. V.

  • Ms. Yoppolo can correct me if I’m wrong, but I think the Processes Supported label refers to the items below it, e.g. the wet clay phase supports the following processes: throwing on the wheel, hand building, and molding elements. The format of the web page makes things a little confusing.

  • Very helpful and interesting; thank you. I had tried wheel thrown porcelain and got some lovely, delicate results but got into trouble turning footrings because of the condition of the clay having made assumptions made that once at hard cheese it is unretrievable! This put me off but now I will definitely give it another go and be a tad more aware of its properties.
    I have seen some lovely sculptural work that involves joining porcelain onto white clay and wonder how that works?
    Mandy D.

  • What chances of firing some porcelain animal figures with very thin legs without them bending? if I lie them down they’ll flop out, too, won’t they? I’ve made one figure supported by two glass jam jars and can’t figure out how to catch the melted glass without losing the independance of the legs of the figure ( v. amateurish,I know!)

  • Shelf supports can be useful. Stack them up till they are the right height. It’s helpful to have a lot of 1/2 inch supports on hand. Alternatively, when you make more animals, how about making some clay supports thicker than the legs, underneath, between the glass jars. Put some thin plastic between them and the figure while they dry so they won’t stick together. Remove the plastic, then fire them. The shrinkage should be the same, and the thicker pieces won’t have as much tendency to collapse in firing.

  • Ann – We’ve made some changes to the layout of the page that hopefully make things a bit more clear! – editor.

  • This is in response to Su’s question about porcelain animals with thin legs. I use Frost porcelain and I make my own design of clay animals. Their legs are not real thin but average. I have not had any problems with them bending. My animals are around 3″ tall. Good luck and let me know how your animal legs work out.

  • I love porcelain!!! I use it for everything. I do handbuilding. I make everything from dinnerware to small animals. I use a myriad of Mason stains in my work and have very good luck avoiding cracking. It does happen tho. I am always open to trying new techniques to save my prized pieces. thanks for this article. I use a Laguna porcelain called Frost. I have read in the comments about other kinds of porcelain. They all seem to have their own personalities.I have a couple of buckets of porcelain that needs to be recycled. I think I am going to try Chris Campbell’s paper clay method once I get around to doing the recycling. Trial and error will prevail!

  • I love porcelain. I’ve worked with both cone 5 and 10 porcelains. There are a few porcelains that I dry really slow by putting them in plastic bins with lids. This evens out the temp and drying process. I also do this when I have thrown pieces and haven’t been able to immediately assemble them. I put the pieces in a bin and assemble them 2-3 days later. One of the hardest porcelains to work with that I have found is Frost by Laguna. It comes in both cone 6 and 10. It cracks easily, needs to be compressed at both the bottoms and sides. The lips also need to be compressed to avoid cracking. Also, I have found that when bisquing, one needs to ramp up very slowly and also soak at the end. I bisque all of my porcelain at cone 04. The results are worth it — the whitest porcelain.

  • This is for Su or anyone else who can use it. I have made dolls and figurines out of cone 6 porcelain slip. The carousel figure legs will be at least partially hollow and everything is thin. I use either alumina hydrate or silica sand sifted onto the shelf first to allow the pieces to slide as they shrink and also to protect the shelf. Then I use a product called “prop” which comes in either a blanket or as something similar to pieces of fluffy wool to support pieces that might slump or bend. It is a little tricky but not that hard. Always allow some leeway for the shrinkage of the porcelain when you prop ie use fluffy pieces that can compress easily. I lay the carousel figures on their sides and put a little bit of the loose prop under the legs that are on the top side or in any other place that needs some support. You can roll pieces of the blanket prop up and put in large openings to help hold them up. I have not used it for bowls etc. yet. All of these products can be reused over and over. Sift the sand or alumina hydrate back into a container. Don’t use both together though. I recall having to fire the A.H. before using it the first time but I have been able to use it over and over. Look in doll making supplies for the prop. Always use a mask when working with any of this stuff. Good luck

  • About the comment regarding warping bowls. I too have faced this issue. Two things to try are: 1) Make the rim thicker than the bowl walls if possible. 2) Dry the bowl with the rim face down. Doesn’t eliminate all problems but it works for me.

    I have also had perfectly round bisqued mugs end up oval after cone 10 firing. I throw very thin and realized my handles were too heavy – thus pulling the mug into oval. Once I lighened up the handles, the problem went away.

  • Gwen,
    I am using a cone 5-6 porcelain and enjoying doing a little water-etching–I find that if it isn’t too thin at the lip that warping is limited tho’ it does still occur. It is just toooo delicious, porcelain, i mean!
    Thank you for sharing your knowledge–it will definitely help me

  • Hiyo! I used to throw porcelain years ago, and learned that the clay particles were more like marbles than platelets, hard to stack up on top of each particle in the clay body. I had to throw fast, up, and pull it into shape without fooling around. Don’t mess around with it while it’s just thrown, but as others have said, work with it in it’s particular stages. Good luck, you-all!

  • I use a 365 cone 6 porcelain body from Ceramic Supply. Is a great throwing body, but do not recommended for hand building. Is translucent when thin, very “rubbery” can be stretched and dried rapidly with heat gun/hair dryer for more complex shapes. Do have problem with cracking around handle attachments, so joint compression and slow drying is recommended.

    For really large thin bowls etc, best to focus on throwing walls of extremely even consistency, thicker rims, and compressing clay with steel rib while throwing, and then achieving thinness by trimming when very leather hard with sharp tool (recommend Bison trimming tools) Also, always throw on bat, handling creates too much distortion and do not wire immediately, let it set on bat until leather hard. Enjoy the whiteness!

  • I’ve only worked with earthenware (handbuilding), but I have a box of porcelain and
    am anxious to try it.
    I’m grateful for all these wonderful tips!

  • What are porcelain cookies? Is it just bisque fired porcelain? Do they keep the bottoms from sticking to the shelves? Can I reuse them?

    Love porcelain and the article. Thanks

  • I worked with porcelain exclusively everyday for three years except for glazing, firing, and maintenance days. I was still working with the porcelain but in other capacities. It was very enjoyable, smooth, sturdy and white. I didn’t have much ‘warping’. But when I did, I did not regard it as a flaw but just the nature of the material.
    If anyone is experiencing ‘warping’, cracking, slumping and etc., and is discouraged, go to a good museum with a very good ceramics collection like The Metropolitan Museum in New York City. It will be opened this Monday for Presidents day. It is usually closed on Mondays. Or go to the Getty Museum in Los Angles. It is free but you must pay for parking. Or search Google or Wikipedia for porcelain, take a good look at the porcelain ware, study the pieces, walk around them when you can, tell me what do you see? I’ll tell you, all of the ‘attributes’ of porcelain. Cracking, slumping and runny glazes. It is just the nature of porcelain ware. Just start or continue experimenting, try out different things to achieve your goals! Just keep working!!

  • Great tips. It is super to have a support base like this to refer to with problems. I use Coleman Porcelain from Laguna. I have experienced some of the problems noted in the responses but porcelain is a an acquired taste, one cannot get out of his mouth. I agree that one should make porcelain the unique clay body in the studio because of the “contamination” factor. Nothing looks, feels, or fires like porcelain and it seems to seek out any other clay body you have EVER used. If every thing in your studio is “porcelainized” you will have less trouble.

  • This is really useful information. I love how glazes look on porcelain, but have also been discouraged by cracking and shrinkage. Thanks for this!

  • Hi, good article, I am throwing porcelain (sorry forgot to say I am in love with it and all its quirkyness), but I am making cake stands, and so far lots of slumping, even firing face down as the stand weight casues the plate to slump in the middle. Do not want to give up but any tips?

  • I have to agree with making porcelain “your focus”, IF that is what you want to master. I work with two products, and two products only, Laguna Frost White Slip, and Laguna Frost 6 clay. I slipcast tons more than I hand build. My handbuilding is limited to decoration for a cast piece. My focus is in altering the slipcast piece once it comes out of the mold.
    There are no other products in my studio, other than glaze and underglazes. I’m still learning every day, but this is what I has chosen to master and it is my my goal to do so. I agree with all of the concerns, problems, issues with this medium but I can tell you that patience is indeed a virtue. I very rarely have any issues with cracking or warping because I practice many of the tips that I read here. I am also a Porcelain Artist, commonly referred to as a “china painter” (hate the term). Learning to paint on glazed porcelain (overglaze decoration) gives me something to do while I’m watching clay dry, or waiting for a kiln to cool down. I love being able to take a piece from concept to completion.
    I have only been doing this for a little over two years now, and I am largely self taught, but it’s what I do all day, every day. Thanks Clayart, and contributors for all you have shared.

  • QESTION: Can I fire “Frost” at a cone .03 and have it vitrified?? Read that it becomes translucent at an cone 5-6.

  • About 10 years ago, I discovered by accident, a way to eradicate ALL my problems that I encountered working with grolleg porcelain. I did share my discovery with a well known porcelain potter and it’s time to give it to the world. If you add 20% or even less cone 10 B mix to your cone 10 grolleg and the wedge the heck out of it (I used a bluebird pugmill), you will have a crack free porcelain body. I even used it for a raku firing of 2 huge jugs I still have here. That led to discovering that porcelain in Raku doesn’t oxidize as quickly as stoneware or raku clay does! One should STILL however, take care of drafts when drying attachments on the porcelain body. Cover it with plastic and let it get to a much drier state that way. Trial and error told me when the handles or attachments were ready to be “exposed” completely to air dry. Kinda like yeast with dough when rising…avoid drafts! Happy trails and good luck because your troubles are over!

  • The graphic that you added at the end really pulled everything together for me. Great advice! Thanks so much for sharing.

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