Bryan on fri 7 dec 01
Are any of the glaze calc programs useful, or better than any other, in
analysing clay bodies?
Bryan
Ron Roy on fri 14 dec 01
Hi Bryan,
Yes they are. Once you know the molecular makeup of a clay body you can
draw certain conclusions about melt and colour.
You must make sure you have real analysis figures to do this. You must not
rely on analysis figures out of most of the books on the market - get em
from the mine and check em regularly - not hard to do these days with web
pages and fax machines.
To give an illustration - I monitor clay bodies for clay manufacturers and
- every once in a while a material is discontinued - lets say an iron
bearing clay.
I had to find a replacement clay and reformulate the bodies with another
clay keeping the colour and melting similar - OK as close to the original
as possible. I found another clay with even more iron in it - reformulated
using calculation - keeping the total iron the same and adjusting the melt
by watching silica and alumina levels. I was amazed that I was able to
duplicate the bodies in one or two tries - and I don't think any potters
noticed - or the diff was not great enough that it made a difference.
There are other tricks of course - try to keep total plastics and non
plastics the same or at least make adjustment in plastics to compensate if
they are raised or lowered.
So I have to say yes because it works for me and I can not imagine having
been able to do it without calculation - certainly not in one try as was
the case when it happened the last time.
What you cannot use is the calculated expansion number - they are not
reliable because of the crystalline nature of clays and the profound role
of quartz and cristobalite in body expansion/contraction.
RR
>Are any of the glaze calc programs useful, or better than any other, in
>analysing clay bodies?
>
>Bryan
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
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