Heloisa Nunes on fri 10 nov 06
Hello, clayarters,
I am in Brazil, struggling with clay here for over a year. I tryied many,
but here things are not as easy as in the US and our clay (south american
Kaolin) is not as good and standards are not always followed. I have had
some problems with some batches of clay, and I am still talking to the
company that makes it to improve plasticity.
I am trying to stick wifv th it because it is the only white clay that has
no "rocks" in it once in a while and my glazes look nicer in it.
However, it is a little short for handbuilding, handles and my extruder. I
do not have a pugmill.
I researched the archives and came up with a few solutions (which my
manufacturer did not know if would work, or thought that may not work).
GLYCERIN
1ml/lb of dry clay - Does it really work? Do people use it regularly? Does
it change the way the clay dries(my manufacturer is affraid of this)? What
is the chemistry of it?Can I add it to wet mixed clay?
EPSON SALTS
I am not sure how to use it
BENTONITE
It seems my manufacturer is affraid the clay may leak more if I add too
much....
Heloisa Nunes on fri 10 nov 06
Sorry, my baby pressed the send buttton...
VINEGAR
Does it change the clay as far as short clays?
Well, this is what I found. I am doing an experiment right now with glycerin
dissolved into vinegar, cutting fine layers of clay and wedging it again
very well. I will leave it in a bag for a few days to see if it changes.
Does anyone can help with this issue? I really appreciate and I look forward
to being able to pull a handle and press a square plate into foam with no
problems!
THank you so much for all the help you always give.
All the best,
Heloisa Nunes
São Paulo, SP Brazil
> Hello, clayarters,
>
> I am in Brazil, struggling with clay here for over a year. I tryied many,
> but here things are not as easy as in the US and our clay (south american
> Kaolin) is not as good and standards are not always followed. I have had
> some problems with some batches of clay, and I am still talking to the
> company that makes it to improve plasticity.
> I am trying to stick wifv th it because it is the only white clay that has
> no "rocks" in it once in a while and my glazes look nicer in it.
> However, it is a little short for handbuilding, handles and my extruder. I
> do not have a pugmill.
> I researched the archives and came up with a few solutions (which my
> manufacturer did not know if would work, or thought that may not work).
> GLYCERIN
> 1ml/lb of dry clay - Does it really work? Do people use it regularly? Does
> it change the way the clay dries(my manufacturer is affraid of this)? What
> is the chemistry of it?Can I add it to wet mixed clay?
> EPSON SALTS
> I am not sure how to use it
> BENTONITE
> It seems my manufacturer is affraid the clay may leak more if I add too
> much....
>
>
>
Timothy Joko-Veltman on sat 11 nov 06
On 11/10/06, Heloisa Nunes wrote:
> Hello, clayarters,
>
> I am in Brazil, struggling with clay here for over a year. I tryied many,
> but here things are not as easy as in the US and our clay (south american
> Kaolin) is not as good and standards are not always followed. I have had
> some problems with some batches of clay, and I am still talking to the
> company that makes it to improve plasticity.
> I am trying to stick wifv th it because it is the only white clay that has
> no "rocks" in it once in a while and my glazes look nicer in it.
> However, it is a little short for handbuilding, handles and my extruder. I
> do not have a pugmill.
Hi Heloisa,
Como vai? Greetings from Brasilia. I'll use English for the benefit
of the list, but I'm curious, what body are you using? I use the
Faria's white body regularly, and have not had any problems with
shortness, nor with pebbles. It is a bit sandy, but nothing
intolerable.
> I researched the archives and came up with a few solutions (which my
> manufacturer did not know if would work, or thought that may not work).
> GLYCERIN
> 1ml/lb of dry clay - Does it really work? Do people use it regularly? Does
> it change the way the clay dries(my manufacturer is affraid of this)? What
> is the chemistry of it?Can I add it to wet mixed clay?
> EPSON SALTS
> I am not sure how to use it
> BENTONITE
> It seems my manufacturer is affraid the clay may leak more if I add too
> much....
I'm not sure what you mean by the clay "leaking", but bentonite is
itself a clay. It has a very small particle size, and adding some to
the mix (a few percent) should make it more plastic, and not
compromise the colour. You can also use ball clays or Argila Sao
Simao. In fact, you may want to suggest/think about using both a bit
of bentonite, a bit of ball clay, and a bit of Argila Sao Simao, that
way, if the quality changes in one, the overall effect on the body
will be less. "A bit" would be about 2% for bentonite, and about 5%
for ball clay and Argila Sao Simao.
I'm not sure about the other solutions ... I had never heard that they
improve plasticity - though I suspect that vinegar could help a bit by
increasing the bacteria count in the body; bacteria are good.
Anyway ... hope that helps.
Um abraco,
Tim
Heloisa Nunes on sun 12 nov 06
Dear Ivor,
Thank you so much for your input. Unfortunatelly, I am not mixing my own
clay. I am buying clay from a company and trying to fix it. It is already
mixed and ready to use, not raw. I am also talking to them about improving
their clay's plasticity (which they are studying).
Materials here in Brazil are a little difficult because standards are not
always followed, and sometimes kaolin changes (and I was told brazilian
kaolin is not as good as north american) and they do not test before they
sell.
Well, I will keep you posted if I find something that works. I really
appreciate your help (I always read your posts with avid interest).
All the best,
Heloisa Nunes,
Sao Paulo, Brazil
Ivor and Olive Lewis on sun 12 nov 06
Dear Heloisa Nunes,=20
You do not tell us what other ingredients you are mixing with your =
Kaolin to make the clay you have been using. Are you following =
instructions from a Potters Text Book or instructions from the people =
who supply your raw ingredients ? Without knowing this it is difficult =
to give guidance.
But in general, one of the propositions about selecting ingredients for =
making Plastic Clay Bodies is to incorporate several types of clay. It =
is also important that the mixture include some form of Flux mineral =
that will assist in the sintering and vitrification processes that =
change your raw materials into a durable strong product.
So your basic mixture will include Kaolin which is a rather coarse =
material, Ball Clay that is very fine and confers plasticity, Potash =
Felspar to ensure good fusion. Bentonite can be added in small =
quantities to enhance plasticity. Silica, quartz flour or ground flint =
is often added to increase the degree of vitrification.
A basic recipe for a white firing plastic clay might be Kaolin 50%, =
Ball Clay 15%, Potash Felspar 25%, Silica 10%.
Vinegar is often recommended to promote the growth of bacteria, which =
is considered by some to make a short clay more plastic. I have not =
heard of Glycerine being used in clay to promote plasticity, though it =
is a wonderful additive to make water base slip or paint flow from a =
brush.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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