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## expansion rate of a glaze

### Llewellyn Kouba on mon 25 feb 02

I have been conversing with someone about a glaze problem/ with the fit of
glass to glaze.
Art wrote .> and glazes, so yes, you will have crazing and cracking. Most
of the
decorative glasses we use, as well as our base glasses have expansion rates

The Question asked and proposed was - 'What is the expansion rate of my
glaze'. I fire to cone 9 range but I have no clue what the expansion rate
of any of my glazes might be? This may very well be a question that is far
over my head and too scientific so I may have to duck out of this one!
yikes. ha My most intelligent reply back might be a simple 'I don't know'
or I don't have a clue.

Llewellyn

### David Hewitt on tue 26 feb 02

Llewellyn,

It is really very simple to calculate the Coefficient of Expansion for

If you would care to go to my web site and click on 'Calculating
Crazing' you will see how this can be done.
http://www.dhpot.demon.co.uk

David

In message , Llewellyn Kouba writes
>I have been conversing with someone about a glaze problem/ with the fit o=
>f
>glass to glaze.
>Art wrote .> and glazes, so yes, you will have crazing and cracking. Most
>of the
>decorative glasses we use, as well as our base glasses have expansion rat=
>es
>
>The Question asked and proposed was - 'What is the expansion rate of my
>glaze'. I fire to cone 9 range but I have no clue what the expansion rate
>of any of my glazes might be? This may very well be a question that is f=
>ar
>over my head and too scientific so I may have to duck out of this one!
>yikes. ha My most intelligent reply back might be a simple 'I don't know=
>'
>or I don't have a clue.
>
>Llewellyn

--
David Hewitt
David Hewitt Pottery ,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk

### Ron Roy on wed 27 feb 02

Dear Llewellyn,

If it is a glossy glaze I can calculate the expansion - most glaze calc
programs have that ability. I need the recipe to do that. I can then tell
you if it high - low or whatever.

All that is dependant on the expansion/contraction of the clay body - it is
the two together that must be taken into consideration.

If you have Mastering Cone 6 Glazes there is a chapter on fit - you will
understand it all - you may have to read it a few times but it is all there

RR

>I have been conversing with someone about a glaze problem/ with the fit of
>glass to glaze.
>Art wrote .> and glazes, so yes, you will have crazing and cracking. Most
>of the
>decorative glasses we use, as well as our base glasses have expansion rates
>
>The Question asked and proposed was - 'What is the expansion rate of my
>glaze'. I fire to cone 9 range but I have no clue what the expansion rate
>of any of my glazes might be? This may very well be a question that is far
>over my head and too scientific so I may have to duck out of this one!
>yikes. ha My most intelligent reply back might be a simple 'I don't know'
>or I don't have a clue.
>
>Llewellyn

Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,