Some Hints on Throwing Porcelain

f the many types of clay, porcelain is the finest -- and the most difficult to 'throw' (form on a potters wheel). Porcelain, an 'artificial' clay, is certainly no matrial for the beginning potter, who would be much better off starting with a more robust clay like stoneware or earthenware.

But there are a few points that can be taken into consideration when throwing porcelain. Porcelain is fairly 'short', i.e. it does not have much plasticity. As it does not have much plastic strength, it also tends to 'flop' easily, especially when too much water has been used, or it is 'overworked'. So it is a good idea to use as little water as possible when throwing porcelain.

Tip 1:

Don't throw porcelain with water; use a porcelain slurry, which will give the necessary lubrication with less water content.

If a piece, let's say a bowl form, is overworkrd, it will tend to flop, i.e. it's walls will collapse. Once this has happened, one might as well start afresh. However cutting the clay off the wheelhead and rekneading it will not always suffice. To regenerate the clay, kneading, letting it rest overnight and then rekneading again is usually a good way to go.

Tip 2:

If a piece looks like it might be getting a bit 'floppy', try working it lightly with a gas burner, an electric paint stripper or even a hairdryer set to 'hot'. This will dry out the clay enough to give it another go. Of course the wheel should be turning while you do this, to ensure an even distribution of the heat.

Generally it will be easier to throw thick-walled pieces than thin-walled ones, but with practice wall thicknesses of about that of a one cent coin or even thinner are possible. This will also depend on the scale of a work -- the larger the piece, the thicker the walls will have to be (to support the weight above).

Tip 3:

Thin walls are not only achieved by throwing, but even more so by turning (cutting off further layers of 'leatherhard' clay with special 'turning' tools).

Another common problem with throwing porcelain is cracking, which can occur during the drying process, or during firing.

Tip 4:

Never let throwing water accumulate in the base of your vessel. Cut a piece of sponge and tie it to the end of a chop stick or something similar. Use this tool to remove any excess throwing water or slurry from the base of your pots.

Cracking is usually caused by uneven compression of the clay (I will not delve into the issue of drying here). Some clays such as raku or coarse earthenwares can be relatively forgiving in this respect, but not porcelain. Uneven compression can result from water accumulating in the base (see Tip 4). More often than not, it is a problem with compressing the clay during centering.

Tip 5:

Center your porcelain on the wheelhead; cut off with a cutting wire; turn around (bash it back onto the wheel upside down) and recenter. This method of centering will ensure that your clay is as compressed on the bottom as it is on the top.

Another problem may happen after throwing the best piece, but then it collapses as you are trying to get it off the wheel. That can be pretty frustrating after putting so much effort into getting it so perfect!

Tip 6:

To ensure your work doesn't collapse when removing it from the wheel, dry it out a bit (evenly and carefully!) with a small burner attached to a portable gas bottle. In fact, with a bit of practice, you can do this to such a fine degree, that you can turn the work immediately on the spot, without first removing it from the wheel.

While these hints are not comprehensive, I hope that they will help one or the other person with their porcelain throwing technique. However theory alone will never be enough -- in this case the old adage "practice makes perfect" certainly does apply!

Happy throwing!

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