wschran@erols.com on mon 13 sep 99
Susi - Go to: www.digitalfire.com/education. There is a good article
about formulating a stable cone 5-7 glossy glaze and link to cone 5 mat.
Bill
Jeanette Smith on fri 8 sep 00
To Becky Gregory in Nashville,
I'm not familiar with the glaze you mention, but it reads like one I'd like
to try.
I wonder if it's the glaze that's the problem. I remember a time years ago
when I, and several other of us would be potters (?) had a similar problem
with Lizella clay. Our teacher (CharlesCounts) told us not to use it because it is
porous, and no glaze would seal it. However we used it anyway
because it was far and away cheaper than any other clay and was good for
practice, but we learned not to make cups and pitchers with that clay.
Maybe your clay didn't get fired high enough to vitrify, or maybe like Lizella,
it is a porous clay. Can you try the glaze on some other clay?
Hope you get good advice from someone on solving your problem. Jeanette
Miccaaa@HOTMAIL.COM wrote:
> Hey everybody! I made a test glaze of the following recipe. Here is
> the problem that I am having with it. I took the Test cylinder,
> filled it with water, no crazing marks, and let it sit for a while to
> see if there was a good fit between my ^6 clay and ^5 glaze. It seems
> that there is not. I still don't see any little hairline cracks from
> the glaze not fitting, but the bottom of the pot is damp and the towel
> underneath it is damp. By damp I mean slightly, cool.
>
> Would you mind looking at this glaze and give me some suggestions?
>
> Smooth Satin ^5
>
> Neph Syenite 45
> Whiting 18
> Kaolin 20
> Zircopax 12
> Silica 5
>
> I really like how smooth the glaze was, and I am wanting to use it as
> a base glaze to develop colored glazes from it. It is a very nice
> clean white glaze.
>
> Thanks to all!
> Becky Gregory in Nashville Tn where it is finally cooled off enough to
> sleep with the windows open.
>
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Miccaaa@HOTMAIL.COM on fri 8 sep 00
Hey everybody! I made a test glaze of the following recipe. Here is
the problem that I am having with it. I took the Test cylinder,
filled it with water, no crazing marks, and let it sit for a while to
see if there was a good fit between my ^6 clay and ^5 glaze. It seems
that there is not. I still don't see any little hairline cracks from
the glaze not fitting, but the bottom of the pot is damp and the towel
underneath it is damp. By damp I mean slightly, cool.
Would you mind looking at this glaze and give me some suggestions?
Smooth Satin ^5
Neph Syenite 45
Whiting 18
Kaolin 20
Zircopax 12
Silica 5
I really like how smooth the glaze was, and I am wanting to use it as
a base glaze to develop colored glazes from it. It is a very nice
clean white glaze.
Thanks to all!
Becky Gregory in Nashville Tn where it is finally cooled off enough to
sleep with the windows open.
Dave Finkelnburg on fri 8 sep 00
Becky,
I had this problem myself and many good ClayArters helped me solve it!
In general, if the bottom of the pot is damp, either moist air is
condensing water onto the pot (not a problem) or the clay isn't vitrified,
which is a problem. In the latter case, just working on the glaze doesn't
really solve the problem. If the clay won't hold water, all by itself, your
glaze is being asked to do more than it should have to do.
Have you tried checking the absorption of your fired clay? To do this,
an unglazed test tile in a glaze firing, and then check to see how much
water it will absorb. You can find references to this test in the archives.
Weigh the tile dry, like just as soon as you take it out of the kiln and
it's still warm, or after you have dried it well in a warm oven. Use a very
accurate scale or a large test tile. Then either soak the tile for 24 hours
in water or boil it for at least a couple hours in water. In the latter
case cool the tile by submerging it in cold water. then pat it dry with a
towel and quickly weigh it again. Finally, calculate the weight gain as
percent, which is = 100 times (wet weight minus dry weight) divided by dry
weight.
Fully vitrified porcelain will absorb almost no water. Properly
vitrified stoneware will absorb less than 3% water by weight, preferably
around 1.5%. If you have more than 3% weight gain from absorbed water, you
probably need to fire hotter to prevent vases from leaking through the
bottom.
Your glaze, by the way, appears to have a fairly high expansion and will
probably craze on most clay bodies. The glaze gurus can help you with
this. You will probably have to use less nepheline syenite and more of some
other flux to reduce the expansion to get a better fit. You can see crazing
best with a glazed test tile which you put in ice water or the freezer, then
put in boiling water, then examine with a magnifying glass of at least 10
power. Do the ice/boil test about 3 times and if you have no cracks, you
have pretty good fit.
I hope this helps!
Dave Finkelnburg, savoring the September sunshine in Idaho
-----Original Message-----
From: Miccaaa@HOTMAIL.COM
To: CLAYART@LSV.CERAMICS.ORG
Date: Friday, September 08, 2000 5:29 AM
Subject: Cone 5 Glaze
>Hey everybody! I made a test glaze of the following recipe. Here is
>the problem that I am having with it. I took the Test cylinder,
>filled it with water, no crazing marks, and let it sit for a while to
>see if there was a good fit between my ^6 clay and ^5 glaze. It seems
>that there is not. I still don't see any little hairline cracks from
>the glaze not fitting, but the bottom of the pot is damp and the towel
>underneath it is damp. By damp I mean slightly, cool.
>
>Would you mind looking at this glaze and give me some suggestions?
>
>Smooth Satin ^5
>
>Neph Syenite 45
>Whiting 18
>Kaolin 20
>Zircopax 12
>Silica 5
>
>I really like how smooth the glaze was, and I am wanting to use it as
>a base glaze to develop colored glazes from it. It is a very nice
>clean white glaze.
>
>Thanks to all!
>Becky Gregory in Nashville Tn where it is finally cooled off enough to
>sleep with the windows open.
Ron Roy on tue 12 sep 00
Hi Becky,
I'm surprised this melts enough to be water proof. Perhaps ypou should try
additions of 5, 10 and 15% frit 3134 - it should still be a matte glaze but
will have a better chance if holding water.
The other part of this is - your clay body is not mature enough to hold
water - thats bad news - what does your clay supplier say about that?
Dave's advice about testing that clay is good.
RR
>Hey everybody! I made a test glaze of the following recipe. Here is
>the problem that I am having with it. I took the Test cylinder,
>filled it with water, no crazing marks, and let it sit for a while to
>see if there was a good fit between my ^6 clay and ^5 glaze. It seems
>that there is not. I still don't see any little hairline cracks from
>the glaze not fitting, but the bottom of the pot is damp and the towel
>underneath it is damp. By damp I mean slightly, cool.
>
>Would you mind looking at this glaze and give me some suggestions?
>
>Smooth Satin ^5
>
>Neph Syenite 45
>Whiting 18
>Kaolin 20
>Zircopax 12
>Silica 5
>
>I really like how smooth the glaze was, and I am wanting to use it as
>a base glaze to develop colored glazes from it. It is a very nice
>clean white glaze.
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
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