C TRIPP on tue 28 aug 01
Part of what Mary wrote:
I mixed the
> glaze by putting all of the dry ingredients through an 80-mesh sieve into
> water, mixing after each small addition of dry ingredients. I then mixed
> with a mixer-attachment on an electric drill after which I adjusted the
> thickness and put the glaze through the 80-mesh sieve again. The glazes
> were allowed to sit for several days and then mixed with the drill
> attachment again before use.
>
Hi Mary,
I am far far from being an expert but I think you can skip the mixing of the
dry ingredients through the seive. In fact, it would be a whole lot safer
to skip this unhealthy and unnecessary dust-making step. Do what Dannon
suggests in her message and that should fix the speckling.
Good luck,
Carol
PS I learned all my glazing mixing skills from the Archives. (I also learned
how to fire my kiln, throw cylinders, understand some glaze chemistry and so
on.) There are all sorts of ideas and tips in that treasure trove.
_______________________________________________________
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Crabtree, Mary B on tue 28 aug 01
A quick question from a pretty new potter and a ClayArt lurker.
I make several glazes by using a commercial transparent base to which I add
oxides, rutile, and superpax for color, opacity, etc. Most of these are
performing very well. However, there are two, one blue and one green, that
I'm having trouble with. When I made the test batches these both turned out
very creamy, solid colors, almost pastel, opaque...very nice. However when
I sized up for a larger batch, I got a pale greenish base with color
speckles in it. Its attractive, but not what I'm looking for. I mixed the
glaze by putting all of the dry ingredients through an 80-mesh sieve into
water, mixing after each small addition of dry ingredients. I then mixed
with a mixer-attachment on an electric drill after which I adjusted the
thickness and put the glaze through the 80-mesh sieve again. The glazes
were allowed to sit for several days and then mixed with the drill
attachment again before use.
So, any suggestions on why I'm getting these 'speckles'? and how to get rid
of them?? I'm thinking that maybe a 120 mesh sieve might do the trick, but
need to order one and thought I'd consult all you glaze gurus in the
meantime..
Both glazes include cobalt oxide, superpax and rutile, and one also includes
chrome oxide. A similar glaze using yellow ochre as the colorant has no
speckling problem. Adding cobalt oxide alone to the transparent base glaze
gives no problems. So, by process of elimination, is there a chance that
either the superpax or the rutile is "sticking" to the oxides, producing
little particles of color that are not dispersed well in the glaze?? (Sorry,
I'm a scientist, although NOT a chemist, so I hate it when I can't figure
out what's going wrong).
Well, any suggestions will be appreciated..
Thanks!!!
And thanks for all the great info shared on Clay Art...I don't post often,
but I learn volumes!!!
Mary Crabtree
Crabtree Pottery
meb3@cdc.gov
Tommy Humphries on tue 28 aug 01
when using cobalt oxide in opaque glazes you will need to ballmill the
glaze,(or just the cobalt) to get rid of the speckles
Tommy
----- Original Message -----
From: "Crabtree, Mary B"
To:
Sent: Tuesday, August 28, 2001 2:21 PM
Subject: color speckles in glaze
> A quick question from a pretty new potter and a ClayArt lurker.
>
> I make several glazes by using a commercial transparent base to which I
add
> oxides, rutile, and superpax for color, opacity, etc. Most of these are
> performing very well. However, there are two, one blue and one green,
that
> I'm having trouble with. When I made the test batches these both turned
out
> very creamy, solid colors, almost pastel, opaque...very nice. However
when
> I sized up for a larger batch, I got a pale greenish base with color
> speckles in it. Its attractive, but not what I'm looking for. I mixed
the
> glaze by putting all of the dry ingredients through an 80-mesh sieve into
> water, mixing after each small addition of dry ingredients. I then mixed
> with a mixer-attachment on an electric drill after which I adjusted the
> thickness and put the glaze through the 80-mesh sieve again. The glazes
> were allowed to sit for several days and then mixed with the drill
> attachment again before use.
>
> So, any suggestions on why I'm getting these 'speckles'? and how to get
rid
> of them?? I'm thinking that maybe a 120 mesh sieve might do the trick,
but
> need to order one and thought I'd consult all you glaze gurus in the
> meantime..
>
> Both glazes include cobalt oxide, superpax and rutile, and one also
includes
> chrome oxide. A similar glaze using yellow ochre as the colorant has no
> speckling problem. Adding cobalt oxide alone to the transparent base
glaze
> gives no problems. So, by process of elimination, is there a chance that
> either the superpax or the rutile is "sticking" to the oxides, producing
> little particles of color that are not dispersed well in the glaze??
(Sorry,
> I'm a scientist, although NOT a chemist, so I hate it when I can't figure
> out what's going wrong).
>
> Well, any suggestions will be appreciated..
>
> Thanks!!!
>
> And thanks for all the great info shared on Clay Art...I don't post often,
> but I learn volumes!!!
>
>
> Mary Crabtree
> Crabtree Pottery
> meb3@cdc.gov
>
>
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>
Dannon Rhudy on tue 28 aug 01
>
....suggestions on why I'm getting these 'speckles'? and how to get rid
>of them??
>Both glazes include cobalt oxide, superpax and rutile, and one also includes
>chrome oxide. ....
Both chrome oxide and cobalt oxide often cause speckling if they are
not seived finely enough -usually 100 mesh will do. When I use
those oxides, I put a cup or two of mixed glaze in the blender
and add the oxides, blend a while, and run them through the
seive into the glaze bucket.
Saves pushing the whole thing through a 100 mesh sieve.
regards
Dannon Rhudy
Edouard Bastarache on tue 28 aug 01
Hello Dannon,
maybe those having problems with granular lithium carbonate
should use your "blender trick".
Later,
Edouard Bastarache
Irreductible Quebecois
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://www.absolutearts.com/portfolios/e/edouardb/
----- Original Message -----
From: Dannon Rhudy
To:
Sent: Tuesday, August 28, 2001 8:31 PM
Subject: Re: color speckles in glaze
Both chrome oxide and cobalt oxide often cause speckling if they are
not seived finely enough -usually 100 mesh will do. When I use
those oxides, I put a cup or two of mixed glaze in the blender
and add the oxides, blend a while, and run them through the
seive into the glaze bucket.
Saves pushing the whole thing through a 100 mesh sieve.
regards
Dannon Rhudy
Paul Lewing on wed 29 aug 01
on 8/29/01 3:58 AM, C TRIPP at CJTripp@EXCITE.COM wrote:
> I am far far from being an expert but I think you can skip the mixing of the
> dry ingredients through the seive. In fact, it would be a whole lot safer
> to skip this unhealthy and unnecessary dust-making step. Do what Dannon
> suggests in her message and that should fix the speckling.
Carol, you should always skip the unhealthy and unnecessary dust-making
step. It's always better to screen your glazes wet.
And I have used that method of breaking up lumps in a blender with barium
carbonate, too. With water, of course.
Paul Lewing, Seattle
Alisa og Claus Clausen on wed 29 aug 01
Dear Mary,
You did the glaze mixing well and letting the glazes sit for a while is
always a good idea.
However I find in general, that oxides tend to speckle more than carbonates.
Could be because the carb. are so much finer to begin with. You can refine
your oxides
with a mortar or pestle, or use the blender idea, that was very good, if
you have a spare or old one.
I use my stalk blender a lot in the studio, but they get very cruddy very
fast, so good thorough
rinsing is necessary to keep them in good working order.
Best regards,
Alisa in Denmark
Dannon Rhudy on wed 29 aug 01
Edouard said:
.......>maybe those having problems with granular lithium carbonate
>should use your "blender trick"........
It works very well indeed for any grainy substances
(well, probably not sand....). I do the same with Tin
Oxide, and now you mention it, lithium.
regards
Dannon Rhudy
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