Mark & Sylvia Mondloch on sat 31 jan 04
AP Green fireclay is no longer available to me which I've always used =
in my clay body recipes so I've been testing new claybody mixes using =
Hawthorn fireclay instead. I ordered the back issue of Studio Potter =
magazine that has an article mentioned on clayart. The article is " =
Cristobalite:The Hump " it's written by Peter Sohngen. In it he tests a =
cone10 stoneware claybody with differing amounts of silica and feldspar =
and has Ron Roy test them on his dilatometer for expansion rates. Very =
interesting!=20
I think I've settled on a general formula and it seems like it might be =
a good time to have my clay body tested for expansion. I'm thinking that =
it would give me a "baseline" to compare to later if a problem should =
crop up with glaze fit or whatever. Also, the expansion curves given in =
the article would give something to compare to now. Before this article, =
I wouldn't have had any idea if the results from Ron were good, bad, or =
ugly.
I think at one time Ron had posted info on how to send him a clay sample =
to test, but I can't find it back for the life of me. So I guess my =
questions for Ron are:
1. Do you even WANT to do this for individual potters?
2. If so, could you post how to prepare a sample, where to send it , and =
cost?
If anyone is interested in the article, it's volume28 number1 available =
from www.studiopotter.org at $7.
Thanks Ron. You're great. ;)
Sylvia =20
---
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake ,Wi 53075
HotArt@silvercreekpottery.com
http://www.silvercreekpottery.com
Ron Roy on mon 2 feb 04
Hi Sylvia,
An interesting part of Peters article - when he used silica that did not
have any microfines in it - or very little - cristobalite was not a
problem. He had to find a source of graded silica and he separated it to be
sure he knew what he was using.
The bags we normally get - marked 200 mesh or 400 mesh have over 95%
microfines - which is the problem.
By the way - we switched from APG to Hawthorn about 20 years ago and it is
a very reliable clay.
Be glad to measure your clay for you - if you include the recipe and the
shrinkage and absorbency I'll do it for $50 US and send you a couple of
charts to compare yours with as well - by fax or mail which ever you want.
Preparing samples for my dilatometer.
Clay:
I need a fired sample (your normal firing cycle) 2 inches long and about
3/8 inch diameter. Make them longer - 3 to 3.5 inches long and I will cut
to length - no glaze.
Make 3 rods of each clay you want measured.
The main things to keep in mind - they need to be smooth and straight. I
recommend rolling a coil with something flat - I use a piece of stiff but
flexible plastic - make sure the coil is even and smooth and straight - dry
in a way that allows no warping - slowly and out of any drafts - under
paper. If you are doing more than one sample mark them with a series of
dots impressed into the clay at the end of the rod with a pencil - don't
forget to roll again to take out any bumps caused by the marking.
Fire and mail to me at RR#4, Brighton, Ontario, Canada. K0K 1H0. Mark the
package SAMPLES - NO Value - otherwise I will be charged for duty and
taxes.
RR
> AP Green fireclay is no longer available to me which I've always used in
>my clay body recipes so I've been testing new claybody mixes using
>Hawthorn fireclay instead. I ordered the back issue of Studio Potter
>magazine that has an article mentioned on clayart. The article is "
>Cristobalite:The Hump " it's written by Peter Sohngen. In it he tests a
>cone10 stoneware claybody with differing amounts of silica and feldspar
>and has Ron Roy test them on his dilatometer for expansion rates. Very
>interesting!
>
>I think I've settled on a general formula and it seems like it might be a
>good time to have my clay body tested for expansion. I'm thinking that it
>would give me a "baseline" to compare to later if a problem should crop up
>with glaze fit or whatever. Also, the expansion curves given in the
>article would give something to compare to now. Before this article, I
>wouldn't have had any idea if the results from Ron were good, bad, or
>ugly.
>
>I think at one time Ron had posted info on how to send him a clay sample
>to test, but I can't find it back for the life of me. So I guess my
>questions for Ron are:
>1. Do you even WANT to do this for individual potters?
>2. If so, could you post how to prepare a sample, where to send it , and cost?
>
>If anyone is interested in the article, it's volume28 number1 available
>from www.studiopotter.org at $7.
>
>Thanks Ron. You're great. ;)
>
>Sylvia
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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