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coe (coefficient of expansion) for porcelain and china

updated thu 15 nov 01


Tom Buck on mon 12 nov 01

Darcy G:
There are no specific COEs that are truly correct for those claybodies
(soft paste porcelain, really porcelaineous stoneware, and hard porcelain,
ie, true porcelain). Not everyone uses the same ingredients, as for
example, in a common mix: 25% each of feldspar, kaolin, ballclay, silica
(flint/quartz). the COEs of such generics will change with location. so
how do you find the actual value: use Jim Robinson's glaze recipes given
in David Beumee's article "Porcelain Bodis for Potters" Cermamics Monthly,
January 1994. Besides, as the makers of claybodies will acknowledge, the
range of particle sizes in a claybody have as much to do with thermal
expansion/contraction as do the individual COEs going into the mix.
good testing. peace. TomB.

Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada

Craig Martell on mon 12 nov 01


The COEs will vary but my cone 10 porcelain has a COE of 5.35 x 10 to the
negative sixth.

regards, Craig Martell in Oregon

Darcy Giesseman on mon 12 nov 01

Does anyone know what the COE (coefficient of expansion) for hard and
soft-paste porcelain/china is and is willing to share it with me?

Thank you.

Darcy Giesseman

David Hewitt on wed 14 nov 01

I can't answer your question precisely but can give an indication of the
likely order of coefficient for a porcelain clay as a few suppliers do
give this information in their catalogues.

I am curious, though, as to the reason for your enquiry as the terms you
use are more those of one dealing with antiques than those of a craft
potter. Are you, for example wanting to make something fit an existing
piece? Is there, perhaps, an interesting story behind your enquiry?

As to the data I do have, the stated coefficient for the porcelain that
I use, as given by Potclays, is 6.417 x10-6/oC
If you wish to see how this compares with other clays you can see the
Potclays table reproduced on my web site under 'Calculating Crazing'
Table 1.

In message , Darcy Giesseman writes
>Does anyone know what the COE (coefficient of expansion) for hard and
>soft-paste porcelain/china is and is willing to share it with me?
>Thank you.
>Darcy Giesseman

David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site