Dave Finkelnburg on wed 14 jun 00
Ron,
I find this thread really informative.
You wrote, ">Boron is very useful for some glazes in the lower stoneware
temperatures
>because it has such a low expansion rate below certain percentages."
Is it possible to say below what % boron has a low expansion? I would
think this would be extremely useful information for formulating mid-range
glazes. Thanks!
Dave Finkelnburg
Ron Roy on tue 20 jun 00
Hi Dave,
The number most often quoted is 12% - keep the boron less than that - if
you are using it to lower expansion. If you want to raise expansion using
boron keep it over 12%.
Boron is not like other oxides - I am thinking it is the elasticity that
boron imparts to a glaze when it's below 12% - which helps fit. I have seen
a chart in Singers book "Ceramic glazes - page 62 - which illustrates the
point.
I have dilatometer charts which tend to confirm this - a boron glaze with a
higher expansion than the clay it's on and I can't get it to craze.
There - you now know what I know about this subject - well not all.
Actually the influence of boron on fit is gradual - not sudden. It works
better as an anti craze when the amount is 10% - better than at 12% and so
on but don't ask for numbers.
RR
> I find this thread really informative.
> You wrote, ">Boron is very useful for some glazes in the lower stoneware
>temperatures
>>because it has such a low expansion rate below certain percentages."
> Is it possible to say below what % boron has a low expansion? I would
>think this would be extremely useful information for formulating mid-range
>glazes. Thanks!
> Dave Finkelnburg
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
| |
|
