Andrea & Armand Grez on fri 28 may 99
Woe is me! I need to resurface all my kiln shelves.
With this latest glaze firing, a red glaze that I splashed all over the
outside of my bowls and mugs jumped...literally...right off and left my
shelves looking like they have the chicken pox!
I know that I have to sand them down, but I don't know how or what to
use. Do I do it by hand or with an electric sander? Belt or disk?
Please help. I need to do a bisque fire, but there is no safe place to
put the ware.
Thank you, Andrea Grez in Richmond, VA
PS After I clean the shelves and reapply the kiln wash, do I have to
fire the shelves before I can use them again? Or can I put the pots on
the wash and fire as usual?
Ellary Blair on thu 28 feb 08
What could make a cone 10 glaze jump off the pot and onto the kiln =
shelves. I do cone 10 crystalline and had my first experience with =
jumping glazes. I do know that dusty or dirty bisque may cause it. I =
think that copper oxide is one of those that do jump. I am wondering if =
it could be temp. related.I usually make sure I have a shelf over all my =
work before I fire it. This time I had to stager and wasn't able to put =
on that last half shelf. Any ideas are welcome.
Ellie Blair
Blair Pottery
www.blairpottery.com
Terrance Lazaroff on fri 29 feb 08
Ellie;
I had this happen to me a few years back and a friend potter told me that
the possible reason for the jumping glaze could be that it was still humid
when I started the firing (one reason to wait a minimum of 24 hours after
glazing to fire). When the temp. passes through 212 degrees it goes all at
once and there is a burst of steam that could disloge your glaze. I was
also told that the glaze and pot may not have been the same temp. when
glazing. If the glaze is too cold it could cause difficulties. I believe
the glaze was too cold as we were having heating problems in the studio and
the glaze was very cold when I mixed it. This could have also resulted in
a slower drying of the glaze.
Terrance
Visit my website http://www.clayart.ca
John Post on fri 29 feb 08
> I do know that dusty or dirty bisque may cause it.
This is something that I always find puzzling. When potters state
that dusty or dirty bisque may cause problems. I think of bisque-ware
as dry by nature and then we dip it into a mixture of dry rocks in
water. When the water evaporates what we are left with is a dry
coating of dusty clay and rocks on a dry piece of bisque. How could a
little dust interfere with the firing of the glaze? I can understand
grease or wax repelling a glaze but a little dust?
John Post
Sterling Heights, Michigan
http://www.johnpost.us :: cone 6 glaze website ::
http://www.wemakeart.org :: elementary art website ::
William & Susan Schran User on fri 29 feb 08
On 2/28/08 10:43 PM, "Ellary Blair" wrote:
> What could make a cone 10 glaze jump off the pot and onto the kiln shelve=
s. I
> do cone 10 crystalline and had my first experience with jumping glazes. =
I do
> know that dusty or dirty bisque may cause it. I think that copper oxide =
is
> one of those that do jump. I am wondering if it could be temp. related.I
> usually make sure I have a shelf over all my work before I fire it. This=
time
> I had to stager and wasn't able to put on that last half shelf. Any idea=
s are
> welcome.
Since the crystalline glazes contain a very high percentage of zinc and a
very minimal amount of clay, one would expect the glaze to crack when dried=
.
This can then lead to crawling that might lead to the glaze "jumping" off
the pot. If you are only wetting the glaze with water, I'd suggest a gum
solution to wet the glaze. Calcining the zinc (just to red heat, 1200=B0 or
so) will help keep the glaze from crawling as it is heated and melts.
Bill
--=20
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Michael McDowell on sat 1 mar 08
Ellie,
I have had problems with jumping glazes in the past. Some of it in the not
too distant past. I suppose that there may be more than one cause and more
than one cure. For me, it has appeared that the glaze was losing adhesion
and leaping from the sides of the pot during the phase of maturation where
there is a lot of boiling disruption in the glaze layer as the glaze begins
to melt into a glass. It is not simply a falling away of glaze poorly
applied. If this is the nature of the problem you are experiencing you may
be able to eliminate the problem by slowing the rate of temperature climb
during that phase. Try limiting temperature climb to no more than 150
degrees Fahrenheit per hour in the range from say 1200 to 1800. See what
that does...
Michael McDowell
Whatcom County, WA, USA
michael@mcdowellpottery.com
http://www.McDowellPottery.com
The Goodsons on sat 1 mar 08
Dear Ellie,
Hello! Oh, I have been there. For me, it had to do with the
coefficient of expansion of my glaze. I do Cone 6 electric glazes, so I
do not know if this will help you since you do cone 10 crystalline, but
I hope that it might. I was using a liner glaze on my functional pieces
that had a very low coefficient of expansion (COE). I am fairly certain
that this was what made my glaze jump!(off the outside of the pieces
right onto the shelves!!) When I corrected the expansion problem, the
glaze stopped jumping. I have never worked with crystalline, so I just
don't know - it is an idea though!
Good luck, I hope you get it to stop jumping soon!!
Linda Goodson
Lincolnton, NC
Ellary Blair wrote:
> What could make a cone 10 glaze jump off the pot and onto the kiln shelves. I do cone 10 crystalline and had my first experience with jumping glazes. I do know that dusty or dirty bisque may cause it. I think that copper oxide is one of those that do jump. I am wondering if it could be temp. related.I usually make sure I have a shelf over all my work before I fire it. This time I had to stager and wasn't able to put on that last half shelf. Any ideas are welcome.
>
> Ellie Blair
> Blair Pottery
> www.blairpottery.com
>
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