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testing glazes..

updated fri 30 jan 98

 

Christi Grame on mon 26 jan 98

Hello,
I've recently quit my "Real" job to be a potter. I have my degree in
Ceramics but it has been almost five years since I've gotten to do anything
so I am really Rusty! As I am starting over I have a couple questions. I
am going to be formulating many test glazes to find those perfect ones and
I need to know how much of each chemical to buy. I don't want to spend
more money then I need to so I was wondering how big of a batch everyone
mixes up for testing. How many grams is the average test batch? Any
pointers would be appreciated.



Thank you!


Christi Grame

rcgrame@midusa.net

**************************************************
* "Imagination is more important than knowledge." *
**************************************************

paul wilmoth on tue 27 jan 98

Christi,

A good amount would be 100 grams which will give you about 2/3 of a
yogurt container.
If you are going to do a liquid line blend , then you will probably want
to start will 400 or 500 gram batches. For this I measure water as well
as material so that the proportions will be more accurate, then I use a
syringe to pull out the desired amount of glaze for the tests ie.
3parts(75%)of glaze A to 1 part (25%) of glaze B, then I do 50-50 then
25-75. This will give a ball park idea of what these glazes will do
together and if necessary you can do a more detailed blending.

good luck - Paul

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Tim Stowell on tue 27 jan 98

If I find come across a recipe that intrigues me for some reason I have
done test batches as small as 100 grams. Usually this is a glaze I'm not
serious about. For glazes that I think we're really going to use or have
definite potential I do a 1000 gram test, this gives me enough to play
with. The problem with doing smaller test batches is that you have to
measure extremely carefully. In a larger test or final mix a slight error
usually doesn't matter, but, in a small test batch a mistake of a few
grams can destroy the test. Good Luck - remember mistakes are ok,
consistency is what matters

Tim - prepping for philly

Tim Stowell Gerard Stowell Pottery
Stacey Gerard 290 River Street
tstwll@juno.com Troy, NY 12180
(518)272-0983

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DONPREY on tue 27 jan 98

Christi,
I do a fair amount of testing and usually make 100 or 200 gram batches.
Anything less than 100 makes it too easy to make significant weighing errors
and doesn't give you much coverage on the test piece. I use 200 if I want to
cover a larger test piece or am testing on more than one clay body.
Don Prey in Oregon

TMartens on tue 27 jan 98

Christy,
Because of the high price of chemicals here, I usually only mix up
500gr dry weight.As this does not make a great deal of glaze I
make little pots that will have the charateristics of big pots. ie
some flat space, upright walls, try to leave a few throwing lines and
then dip as usual.So far tests done on these little pots have worked
out OK. I then also have a flat piece on which I do line blends of
the different glazes I have mixed to see which react well with each
other........
Hope this is of some help
Toni Martens, Durban South Africa where the weather is far too hot
and humid for human consumption!

Lili Krakowski on thu 29 jan 98

Glazes run in families: Calcium-borate, magnesium, feldspathic--and you
probably like a certain look and you probably fire at a specific cone. My
suggestion is that you lay in fair amounts of kaolin (which I think better
for glazes) a soda spar, a potash spar, dolomite or pure magnesium (though
I prefer talc) whiting (though I prefer wollastonite) some zinc and
possibly some strontium, ad a basic frit like 3124. THEN start
testing.DON'T buy everything at once. There is plenty of time to move on.
Later you might want some red and ball clays to try slip glazes; but for
now just limit your testing to glazes that are said to have the look you
want, and fire to the cone you want. Normally glazes are weighed out for
testing in 100 gm lots (3.+ ounces) which is good: becaue you will want to
do some blends. I would also sugggest you get COOPER'S book called
glazes, and a compendium of glazes (just recipes) of his which I don't
remember the title of, but a supplier like Axner, or The Potters'SHop
will know. What is a fair amount? Well that depends on the space you
have, and the amount you mean to produce. A five gallon bucket takes
about 5K (about 11 lbs) of mixed up (fluid glaze) take it from there.

Good luck.



On Mon, 26 Jan 1998, Christi Grame wrote:

> ----------------------------Original message----------------------------
> Hello,
> I've recently quit my "Real" job to be a potter. I have my degree in
> Ceramics but it has been almost five years since I've gotten to do anything
> so I am really Rusty! As I am starting over I have a couple questions. I
> am going to be formulating many test glazes to find those perfect ones and
> I need to know how much of each chemical to buy. I don't want to spend
> more money then I need to so I was wondering how big of a batch everyone
> mixes up for testing. How many grams is the average test batch? Any
> pointers would be appreciated.
>
>
>
> Thank you!
>
>
> Christi Grame
>
> rcgrame@midusa.net
>
> **************************************************
> * "Imagination is more important than knowledge." *
> **************************************************
>

Lili Krakowski