Martin Rice on tue 19 mar 02
As many of you know (because you've been helping me so much) I'm trying =
to develop a low-mid-range (cone 2-3) claybody and looking for glaze =
recipes in the same range. While trying to find the necessary =
ingredients for the ideas many of you have sent me, I also had another =
thought today (I have one once a day, whether I need it or not).
I'm using a red clay which I buy from a from a factory here that is =
owned by the biggest pottery in the country. The clay has good =
plasticity and is quite groggy. Yesterday, I went to the factory and =
asked them what they put into it. The guy in charge says that they add =
absolutely nothing other than water.
I watched them for awhile and what they do is fill very large wooden =
rectangles on the ground (look like the outsides of raised garden beds) =
with the liquid clay. Men are raking it and stirring it and some of the =
rectangles seem to be drying. At the same time there's a concrete area =
where there are hundreds of "cow pies" of the clay, also drying. When I =
buy it it's in 50 lb. cylinders in plastic bags.
Then I went to the pottery. They know me well there because I've been a =
good customer -- they've made a lot of custom items for me such as =
outside lights that are mounted on walls. But yesterday I asked if I =
could go in back to where the potter's were working and they graciously =
agreed. Wow, what a sight for me who has never seen production potters =
at work!
When I was there there were only three of them working, and they were =
extremely friendly and nice. We had a good laugh when I told them that =
this was a hobby for me. They said that a hobby for them is playing =
football and tennis.
Here I go finally getting to the point. I asked them what temperature =
they bisqued at. They said cone 06. They also said that at even cone 05 =
the pieces would distort. They also glaze at 06 (though most of the =
things they sell are decorative and unglazed. The glazed pieces are =
always, as far as I can tell, matt.
So what what my idea was and what I'm asking (I hope this isn't the =
dumbest thing you've ever heard) is whether I can add anything to this =
clay to bring it up to a cone 2-3 level? (Cringe.) If so, what might it =
be and what might the proportions be? And, if so, would I put the =
claybody in water and let it get really soft (but not slip -- or maybe =
slip) before adding other ingredients?
Thanks so much,
Martin
Lagunas de Bar=FA, Costa Rica
www.rice-family.org
Ababi on wed 20 mar 02
Dear Martin, it might surprise you but it is not a dumb question.
Offer one Try yourself above a plate perhaps it survives?
Offer two: Add grog, try 10%
For a long time I did not teach I was stuck with 250K'g of low fire
clay. It led me to work with paperclay.
I offer you to buy and learn Rosette Gault's new book about Paperclay
Here is her Email rosette@paperclayart.com
Her site is http://www.paperclayart.com/index.html
Do not miss Graham Hay's site http://www.grahamhay.com.au/
I find paperclay very useful to my work. if you need further advises I
shall give you.
I have a ^06 clay that works wonderful in ^04
Do not hesitate to ask "dumb" question!
Ababi Sharon
Kibbutz Shoval- Israel
Going deeply into glazing
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
http://www.israelceramics.org/
---------- Original Message ----------
>So what what my idea was and what I'm asking (I hope this isn't the
>dumbest thing you've ever heard) is whether I can add anything to this
>clay to bring it up to a cone 2-3 level? (Cringe.) If so, what might
>it be and what might the proportions be? And, if so, would I put the
>claybody in water and let it get really soft (but not slip -- or maybe
>slip) before adding other ingredients?
>Thanks so much,
>Martin
>Lagunas de Bar=FA, Costa Rica
>www.rice-family.org
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Craig Martell on wed 20 mar 02
Hello Martin:
Have you tried this clay in the cone 2-3 range? It might be a good thing
to give this a try before making changes to the clay. If it worked you
would eliminate a lot of labor. I would proceed with caution and do some
tests with protection for your shelves in case the clay starts to get
fluid. You might also fire some tests to cone 05 and then do an absorbtion
test of the fired pieces to see just where the vitrification is at. If you
are at or near zero percent absorbed water then taking this clay to cone
2-3 would not be advisable.
If you want to use local materials, I would look for a more refractory clay
and then try some additions by weight to determine the amount needed to
bring the clay into the cone 2-3 range that you want. What I would try is
mixing a known weight of the new clay with a known weight or volume of
water to bring it to the consistency that you think is good for
workability. Then add this to the red clay in a line blend, pound per
pound ratio. Start with 9 lbs red to 1 lb new clay, then 8 lbs red to 2
lbs new and so on until your fired samples give you the mix that you want.
The big problem here is that you're dealing with a red clay that can't be
altered as is, without the addition of something else. It's already
adequately fluxed to be mature in the low fire range. So, not being able
to take anything out, you have to add something to bring the maturation
temp up. I suggested a more refractory clay because this has less of a
chance of altering the working properties of the clay. You could add some
alumina and or silica to the clay and this would increase the maturation
point but would make the claybody less plastic and would also change the
glaze fit properties. However, the glaze fit could change for the better
but you won't know until you do some tests.
I have no idea what is available to you in the way of raw materials. If
you could get some kaolin or stoneware clay, either would be an addition
that would move things in the right direction. I know that you can get EPK
in Mexico City but I don't know what's available in Central America.
regards, Craig Martell in Oregon
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