Lee Love on tue 8 jul 08
On Tue, Jul 8, 2008 at 10:49 AM, Leigh Whitaker wrote:
> glaze that is being treated badly?
>
Glass always breaks when you hit it on something hard.
--
Lee Love in Minneapolis
http://mashikopots.blogspot.com/
http://claycraft.blogspot.com/
"Let the beauty we love be what we do.
There are hundreds of ways to kneel and kiss the ground." --Rumi
Leigh Whitaker on tue 8 jul 08
I posted this over on potterybasics too, so if you are a member of both
lists you've seen this before.
I had been having some off and on problems with glaze crazing and I think
the issue (this time) was that I didn't mix my glaze well enough after it sat
for a couple of weeks.
So, that seems to be fixed. I resieved the glaze a few times and also mixed
up a new batch with a slightly lower coefficient of expansion. Neither of
them crazed, so that's great.
**Now I have another question. I have been tapping my pieces on the side of
my sink to make sure that they don't shiver. If I do this about 3 times in
the same spot, with a fair amount of pressure I do get a crack in the glaze.
The glaze doesn't shiver, in that no sharp slivers break off. Is that
cracking with being stuck a problem with fit or is that just normal behavior for a
glaze that is being treated badly?
Thanks!
Leigh Whitaker
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Ron Roy on sat 12 jul 08
Hi Leigh,
There are tests to see if ware will eventually craze - like heating and
then cooling quickly - but they are unreliable because of the thermal shock
aspect.
Try 10 cycles of boiling water to ice water - like dipping into boiling
then dipping into ice water - that should at least tell you if they will
craze in a year or so.
If you send me the recipes you are working with I can perhaps give you my
opinion based on my experiments.
RR
>I posted this over on potterybasics too, so if you are a member of both
>lists you've seen this before.
>
>
>I had been having some off and on problems with glaze crazing and I think
>the issue (this time) was that I didn't mix my glaze well enough after it sat
>for a couple of weeks.
>
>So, that seems to be fixed. I resieved the glaze a few times and also mixed
>up a new batch with a slightly lower coefficient of expansion. Neither of
>them crazed, so that's great.
>
>**Now I have another question. I have been tapping my pieces on the side of
>my sink to make sure that they don't shiver. If I do this about 3 times in
>the same spot, with a fair amount of pressure I do get a crack in the glaze.
>The glaze doesn't shiver, in that no sharp slivers break off. Is that
>cracking with being stuck a problem with fit or is that just normal
>behavior for a
>glaze that is being treated badly?
>
>Thanks!
>
>
>Leigh Whitaker
Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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