Randy McCall on sat 14 feb 04
I would appreciate some advice on adjusting a glaze. This is a Cone 6
glaze.
I got a glaze from Chris Schafale. The base is
3134 50%
Kaolin 25%
Silica 25%
This is a nice shiny, smooth glaze with coloring oxides, but I would like to
adjust it some for brushability.
I want to change it to the following
3134 25%
GB 25%
Kaolin 25%
Silica 25%
Do you think this will give close to the same glaze and increase
brushability. I have always liked the way glazes heavy in GB brushed on
giving the piece a smooth even coat.
Appreciate any recommendations.
Randy
Ivor and Olive Lewis on sun 15 feb 04
Dear Randy McCall,
I am of the opinion that adding 25% Gerstly borate will have a marked
effect on the character of your glaze, as will removing 25% 3134
Frit.
Brushability is a function of the vehicle which you mix into your
glaze to give its liquid quality. This will be water.
So you have to change the character of your water with something which
will be neutral towards the chemistry of your glaze when it melts, so
no Sodium silicate.
Three things. A flow agent such as Glycerine is helpful to make the
slurry flow freely from the brush. An adhesive to make it stick well
once it is in place, such as Gum Arabic or one of the polyvinyl or
acrylic painting agents. A thickener such as CMC, which could serve as
an adhesive anyway.
Do some experiments to find the optimum qualities to suit your
situation.
Best regards,
Ivor Lewis. Redhill, South Australia
Ababi Sharon on sun 15 feb 04
Hello Randy
Very briefly without any analysis in order to have the same results try
first the same recipe.
Instead of 25 kaolin use 20 kaolin and 4-4.5% calcined kaolin. Or make
it 15 kaolin and 8-9% calcined kaolin.
GB for 3134 one for one works in the stories.
You calcine the kaolin in two ways: Either add to a bisque firing in a
bisqued ware than sieve it well, or fire it by it selves to 825C which
is 1517F. In this case it will be fire faster and will be easier to
sieve.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://ababi.active.co.il
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
To Ceramics forum in Hebrew:
http://www.botzpottery.co.il/kishurim.html
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Randy
McCall
Sent: Saturday, February 14, 2004 10:43 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Adjusting a Glaze?
I would appreciate some advice on adjusting a glaze. This is a Cone 6
glaze.
I got a glaze from Chris Schafale. The base is
3134 50%
Kaolin 25%
Silica 25%
This is a nice shiny, smooth glaze with coloring oxides, but I would
like to
adjust it some for brushability.
I want to change it to the following
3134 25%
GB 25%
Kaolin 25%
Silica 25%
Do you think this will give close to the same glaze and increase
brushability. I have always liked the way glazes heavy in GB brushed on
giving the piece a smooth even coat.
Appreciate any recommendations.
.
Linda Pahl on sun 15 feb 04
OK. Let me try this again (I've got to learn to slow down and double
check myself *before* clicking "send" as there were a couple of
inaccuracies in my original response).
Randy McCall wrote:
>
> I got a glaze from Chris Schafale. The base is
> 3134 50%
> Kaolin 25%
> Silica 25%
>
> This is a nice shiny, smooth glaze with coloring oxides, but I would
> like to
> adjust it some for brushability.
>
> I want to change it to the following
>
> 3134 25%
> GB 25%
> Kaolin 25%
> Silica 25%
>
> Do you think this will give close to the same glaze and increase
> brushability?
> Randy
>
Hi, Randy,
I wouldn't change the composition of the recipe at all so as not to
change the glaze's character.
Instead, when I know I'm going to use a glaze just to brush on, I add
.5 grams (that's *point* five grams) of CMC per 100 grams of the recipe
as it improves brush-ability of the glaze.
For me, it works very well as the CMC helps the glaze stay wet longer
to allow for an even flow during brushing. CMC also seems to help the
glaze adhere well to the pot so that when it dries it is not so powdery
and does not easily transfer to your hands as you handle it.
(CMC is available at most ceramic suppliers.)
Best,
Linda
Linda Pahl on sun 15 feb 04
Randy McCall wrote:
>
> I got a glaze from Chris Schafale. The base is
> 3134 50%
> Kaolin 25%
> Silica 25%
>
> This is a nice shiny, smooth glaze with coloring oxides, but I would
> like to
> adjust it some for brushability.
>
> I want to change it to the following
>
> 3134 25%
> GB 25%
> Kaolin 25%
> Silica 25%
>
> Do you think this will give close to the same glaze and increase
> brushability?
> Randy
>
Hi, Randy,
I wouldn't change the composition of the recipe at all so as not to
change the glaze's character. Instead, when I know I'm going to use a
glaze just to brush on, I add .5% (that's *point* five percent) of CMC
per 100 grams of the recipe as it improves brush-ability of the glaze.
For me, it works very well as the CMC reduces the drying time of the
glaze to allow for an even flow during brushing. CMC is available at
most ceramic suppliers.
Best,
Linda
Ron Roy on mon 16 feb 04
Hey Randy,
Your adjusted glaze is not too far off fron the original - I calculated it
with an analysis of old GB for starters - it's close but has less silica.
If you are using new GB it may be quite a bit off - so I cannot venture a
guess because I don't have the analysis for the GB you are using.
The expansion of all these glazes is low - I would alter that glaze to have
more KNaO to raise the expansion.
The expansion with the newer - more refractory GB - is even lower - better
look before you leap.
RR
>I would appreciate some advice on adjusting a glaze. This is a Cone 6
>glaze.
>
>I got a glaze from Chris Schafale. The base is
>3134 50%
>Kaolin 25%
>Silica 25%
>
>This is a nice shiny, smooth glaze with coloring oxides, but I would like to
>adjust it some for brushability.
>
>I want to change it to the following
>
>3134 25%
>GB 25%
>Kaolin 25%
>Silica 25%
>
>Do you think this will give close to the same glaze and increase
>brushability. I have always liked the way glazes heavy in GB brushed on
>giving the piece a smooth even coat.
>
>Appreciate any recommendations.
>
>Randy
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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