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what happens if i fireglaze ^2 at ^6?

updated sun 5 oct 03

 

Adriana on fri 3 oct 03


My problem: I don't have a kiln, so I have to rent studio space. They
bisque fire at ^06, which is fine with the clays that I have. However;
they do the glaze firing at ^6, (2250=B0). The clays that I used are Malone
Red and Terracotta with Grog. I did sculptures 2 1/2" ft H. as well as
tiles. The problem is that the recommended Virtification is ^2 (2075=B0). I
want to know what happens to the piece if I glaze them with glazes for ^6
and fire it at ^6 as opposed to the recommended ^2? THANKs for any
insights.

Craig Dunn Clark on fri 3 oct 03


Adriana, check with manufacturer of the Malone Red. If it is a stoneware
clay body it may very well take the temp of a cone six glaze firing. As to
the terra cotta...chances are that is specifically made as a low fire clay
body chock full o iron. Unless it is some type of quasi terra cotta body
which is acutally a stone ware body made to look like terra cotta when
fired. If it is indeed the real macoy and you overfire it to a cone six you
will end up with glaze faults galore, body blotting and slumping at best. At
the worst you will end up with a semi-melted mass of what was once your
sculpture melted to the kiln shelf (this will not please whoever owns the
kiln.) To be sure check with the clay manufacturer and tell them what you
intend to do.
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org

----- Original Message -----
From: "Adriana"
To:
Sent: Friday, October 03, 2003 4:01 PM
Subject: What happens if I fireglaze ^2 at ^6?


My problem: I don't have a kiln, so I have to rent studio space. They
bisque fire at ^06, which is fine with the clays that I have. However;
they do the glaze firing at ^6, (2250). The clays that I used are Malone
Red and Terracotta with Grog. I did sculptures 2 1/2" ft H. as well as
tiles. The problem is that the recommended Virtification is ^2 (2075). I
want to know what happens to the piece if I glaze them with glazes for ^6
and fire it at ^6 as opposed to the recommended ^2? THANKs for any
insights.

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piedpotterhamelin@COMCAST.NET on fri 3 oct 03


HI.
To be specific in answering your question, you must do the work yourself.
Make some quick test samples that duplicate the large pieces in the manner that you make them and have them fired up to cone 6 both with your glaze and unglazed. I would advise to place these on broken kiln shelves as if they are truly cone 2 clays they have the potential to fuse to the shelf where they stand (and you will need to chip them off) and at the worst, to slump and collapse. By the way, any air pockets would expand in the clay like blisters, called blebbing.
If you don't have this problem, you still would have increased shrinkage and the possibility of your glaze surface becoming fluid (if they also are cone 2) and flowing off the pot onto the shelf below. Fusing the mess to the shelf. If you have a cone 6 glaze on this clay body, it could fuse more completely into the clay, looking more rock like and loosing the qualities that you admired.
Test it out before you lose your prized items.
I am unfamiliar with this clay and since you didn't state the source, I could not look up a web catalog.
Stay happy
Good luck
Rick

--
"Many a wiser men than I hath

Chris Schafale on sat 4 oct 03


Methinks it would be safer to use lowfire glazes and do
the glaze fire at 06....

Chris


My problem: I don't have a kiln, so I have to rent studio
space. They
bisque fire at ^06, which is fine with the clays that I
have. However;
they do the glaze firing at ^6, (2250=B0). The clays that I
used are Malone
Red and Terracotta with Grog. I did sculptures 2 1/2" ft
H. as well as
tiles. The problem is that the recommended Virtification
is ^2 (2075=B0). I
want to know what happens to the piece if I glaze them
with glazes for ^6
and fire it at ^6 as opposed to the recommended ^2?
THANKs for any
insights.
Light One Candle Pottery
Fuquay-Varina, North Carolina, USA
(south of Raleigh)
candle@intrex.net
http://www.lightonecandle.com

Snail Scott on sat 4 oct 03


At 05:01 PM 10/3/03 -0400, you wrote:
>...I
>want to know what happens to the piece if I glaze them with glazes for ^6
>and fire it at ^6 as opposed to the recommended ^2?


Probably warping or bloating. The only way to be
sure is to fire some. Make a sort of bridge-shaped
structure, about as thin as the work you made.
Put it on a slab made of ^6 clay and fire it to ^6.
Inspect it after firing.

Odds are, though, that medium-to-large-sized work
won't survive ^6 without at least some warping.

Could you make enough work to fill the whole kiln,
and ask for a 'special' firing to ^2? They might
ask you to buy the cones, since it's probably not a
temperature they keep in stock, but that's no big
cost, and it should be no hardship for them to fire
lower anyway.

Otherwise, get some low-fire glazes (or non-glaze
surface materials like oxides, underglaze, etc) and
do your final firing to ^06. If it gets fired together
with greenware in a bisque firing, glazes like the
low-fire reds and oranges may burn out, but others
will be fine. Oxides and underglazes will also be
fine, and unless the piece is going outdoors, paint
might be a great surface choice, too.

Unless you have a huge stockpile of this ^2 clay,
I'd forget it and get some ^6 stuff. Clay is cheap,
compared with the labor of making something that
can't be properly fired.

-Snail