Alisa and Claus Clausen on wed 8 mar 00
------------------
I think I've got it=21
Todays kiln load was fine, with all the transparent glaze hanging to the =
pots
and
no shivering. Well, only a couple hours out of the kiln, so I am not =
completely
in the safe zone yet.
The glaze was mixed and I measured the viscosity. I watered it down to =
right on
40 where it
is recommended to be. It seems to hold. My guess is that the only problem =
I
was having
is that the glaze was too thick. People in the studio can be lazy about =
mixing
up the
buckets and almost never measure. In fact I never really measured more than=
the
=22knuckle=22 test with my own glazes, but I know them. In the community =
studio I
have
routinely checked fresh mixed glazes with a visosity meter. But some glazes=
are
used more often than others and those others can settle and thicken quickly.
I have looked at combinations of these slips on 4 different bodies that I =
tried
and there no
bad fit problems. I became suspicious of the white body because it is used
widely
in the community studio. But now I am much more apt to think that all this
shivering
is due to a too thick application of a very touchy glaze. Which also makes =
me
think
we should find a more stable transparent glaze for the comminity studio.
Any other ideas, still welcome.
Thanks
Alisa in Denmark
Paul Taylor on fri 10 mar 00
Dear Alisa
I think the body fitted the glaze well even though the glaze was under a
little strain. This compression probably added to the strength of the pot.
However when the slip was added the glaze body layer was disturbed and
the glaze becomes less laminated to the body by the glaze body layer thus it
flakes off especially if for some reason a small amount of flux is missing
in the slip. That is the trouble with slips they are notoriously difficult
to get a fit and they also show up faults all round. A thin slip you may get
away with because the laminations are small and the glaze could melt its way
through the slip and join the body in places.
A thick glaze will also exasperate problems especially on nice rolled
rims to avoid these industry and the Ting ware makers put their glazes on
thin. But that avoids crazing ! Maybe it will avoid shivering and pinholing
as well.
The Chinese practice of putting on several thin layers may have been to
avoid such problems small layers adding flexibility to the glazes.
Regards paul T
I hope I am as acredited for the good ideas as the bad ones.
Have a cold and nothing to do but bother you.
----------
>From: Alisa and Claus Clausen
>To: CLAYART@LSV.UKY.EDU
>Subject: Answering my engobe shivering problem
>Date: Wed, Mar 8, 2000, 10:44 pm
>
>----------------------------Original message----------------------------
>------------------
>I think I've got it!
>Todays kiln load was fine, with all the transparent glaze hanging to the pots
>and
>no shivering. Well, only a couple hours out of the kiln, so I am not completel
>in the safe zone yet.
>
>The glaze was mixed and I measured the viscosity. I watered it down to right o
>40 where it
>is recommended to be. It seems to hold. My guess is that the only problem I
>was having
>is that the glaze was too thick. People in the studio can be lazy about mixing
>up the
>buckets and almost never measure. In fact I never really measured more than th
>"knuckle" test with my own glazes, but I know them. In the community studio I
>have
>routinely checked fresh mixed glazes with a visosity meter. But some glazes ar
>used more often than others and those others can settle and thicken quickly.
>
>I have looked at combinations of these slips on 4 different bodies that I tried
>and there no
>bad fit problems. I became suspicious of the white body because it is used
>widely
>in the community studio. But now I am much more apt to think that all this
>shivering
>is due to a too thick application of a very touchy glaze. Which also makes me
>think
>we should find a more stable transparent glaze for the comminity studio.
>
>Any other ideas, still welcome.
>Thanks
>Alisa in Denmark
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