Snail Scott on mon 1 sep 03
At 02:34 PM 9/1/03 EDT, you wrote:
>...run into several problems...I'm not use to using frits as a base, it
doesn't have that creamy feel
>to it that the commercial glazes have.
Lots of commercial glazes use frit, too. Adding
bentonite will help with suspension (notoriously
a pain with high-frit glazes), and adding CMC
gum will give you the creamier texture.
>...electric kilns at my school cannot go up to ^ 5 & 6...
>when I tried the MC6G glazes in there
>-- whoa, disaster. I think I am the only one at school who doesn't mind
>grinding shelves...
I'm confused...why did the shelves need grinding
if the kiln didn't reach temperature?
By the way, the commonest reason why a kiln
won't hit temperature is tired elements. Turn
on the kiln to 'hi' for about 15 minutes, then
look in the peepholes. Are any of the elements
not red, or red only in patchy spots? I know
budgets are tight everywhere, but replacing
just a few of the elements might cure the
problem. Just one bad element is enough to
prevent a kiln from reaching ^6.
-Snail
Imbolchottie@AOL.COM on mon 1 sep 03
OK, ^ 6 glaze firings. I've been using MC6G (Mastering Cone 6 Glazes) but
have run into several problems. One was suspension -- and I think bentonite, or
Epsom salts, would help in that area. Plus I have screen the daylights out
of it. I'm not use to using frits as a base, it doesn't have that creamy feel
to it that the commercial glazes have.
And kilns -- the electric kilns at my school cannot go up to ^ 5 & 6, they
are tired beasts, as well as ancient. So when I tried the MC6G glazes in there
-- whoa, disaster. I think I am the only one at school who doesn't mind
grinding shelves. So using the electric kilns is out the question for MC6G...darn.
Gas firings -- again another stumbling block. We have one kiln that has two
sets of rings. One set for the four corners (outer ring) and another set of
six, three in front, three in back (inner rings). This kiln is notorious for
uneven firings.
Is it possible to be doing a reduction firing and an oxidation firing in the
same kiln at the same time?
My witness cones on the bottom (08/4/5) bend while the cones at the top
barely start to bend. I closed the flu to the point of holding in heat, yet not
having flames leaping out (reduction). I'll be damned if the pieces on the top
were reduced. One green will reduce to a silver tone under reduction. Pieces
on the top were silver. Same green middle of kiln and on the edge of the
kiln shelf -- the beautiful green from oxidation. If they were in the middle of
the shelf, I could see it, but they weren't, they were on the edge of the
shelf.
One suggestion I got was to only use the inner ring of burners - 6 is enough
burners, but 10 isn't necessary.
I wish we had a small gas test kiln, but we don't. I am, a heart, a
reduction firing kind of guy. When I see that green flame licking the sky I get that
giggly wiggly dance going on inside me -- not quite dancing naked under the
moon, but close.
I'm stumped and open to any, and all, responses. I admit this Glaze Quest
has been the hardest part of my education in ceramics but well worth it. I read
somewhere that there are a limited number of shapes one can throw on the
wheel, but surface treatment is where it's at.
So much to learn, what fun it is.
Jonathan in LA
Snail Scott on tue 2 sep 03
At 02:42 PM 9/2/03 -0700, you wrote:
>...Is there any
>reason you couldn't just turn it on for 15 minutes with the lid open?
>It would give you a better idea than using the peepholes, especially
>if there were "patchy spots"...
I do leave the lid open when I check mine. I
just didn't want to recommend it for a school
setting like the one described. Institutions
can be touchy about safety when students are
involved, not entirely without reason.
-Snail
Mary White on tue 2 sep 03
>By the way, the commonest reason why a kiln
>won't hit temperature is tired elements. Turn
>on the kiln to 'hi' for about 15 minutes, then
>look in the peepholes. Are any of the elements
>not red, or red only in patchy spots? I know
>budgets are tight everywhere, but replacing
>just a few of the elements might cure the
>problem. Just one bad element is enough to
>prevent a kiln from reaching ^6.
>
> -Snail
I was thinking I should have a look at my elements. Is there any
reason you couldn't just turn it on for 15 minutes with the lid open?
It would give you a better idea than using the peepholes, especially
if there were "patchy spots".
Mary
Ron Roy on wed 3 sep 03
Hi Jonathan,
I find this quite puzzling - our glazes are supposed to be fired at cone 6
in oxidation - and several people have written about how well suspended
they are.
So here am I trying desperately, to understand what has gone wrong - so I
need you to answer some questions.
How are you ascertaining the thickness of the glaze in the bucket?
How are you apply glaze?
Your remark about grinding shelves - did the glaze fall off the ware during
the firing?
The gas kiln - it is possible to have an oxidizing atmosphere and a
reducing atmosphere in the same kiln but it would be hard to control and
certainly the temperatures would be different is each area. Not recommended
because there will be some areas where the ware will be both reduced and
oxidized.
I think that is an up draft kiln and others on this list will be better
able to advise on how to fire it more evenly - it is difficult but possible
I think.
Our glazes are not tested for reduction although some should be fine. The
ones with high iron content will tend to run for sure in reduction -
especially the waterfall.
Which glazes are you using?
Some who should know have stated they thought some of our glazes looked
like reduction fired even though they were oxidation fired - slow cooling
is the key there - hard to do in an updraft I suspect.
Let John and I know what is happening Jonathan - we want to help - and we
want to know how any of our glazes work in reduction.
RR
>OK, ^ 6 glaze firings. I've been using MC6G (Mastering Cone 6 Glazes) but
>have run into several problems. One was suspension -- and I think
>bentonite, or
>Epsom salts, would help in that area. Plus I have screen the daylights out
>of it. I'm not use to using frits as a base, it doesn't have that creamy feel
>to it that the commercial glazes have.
>
>And kilns -- the electric kilns at my school cannot go up to ^ 5 & 6, they
>are tired beasts, as well as ancient. So when I tried the MC6G glazes in there
>-- whoa, disaster. I think I am the only one at school who doesn't mind
>grinding shelves. So using the electric kilns is out the question for
>MC6G...darn.
>
>Gas firings -- again another stumbling block. We have one kiln that has two
>sets of rings. One set for the four corners (outer ring) and another set of
>six, three in front, three in back (inner rings). This kiln is notorious for
>uneven firings.
>
>Is it possible to be doing a reduction firing and an oxidation firing in the
>same kiln at the same time?
>
>My witness cones on the bottom (08/4/5) bend while the cones at the top
>barely start to bend. I closed the flu to the point of holding in heat,
>yet not
>having flames leaping out (reduction). I'll be damned if the pieces on the top
>were reduced. One green will reduce to a silver tone under reduction. Pieces
>on the top were silver. Same green middle of kiln and on the edge of the
>kiln shelf -- the beautiful green from oxidation. If they were in the
>middle of
>the shelf, I could see it, but they weren't, they were on the edge of the
>shelf.
>
>One suggestion I got was to only use the inner ring of burners - 6 is enough
>burners, but 10 isn't necessary.
>
>I wish we had a small gas test kiln, but we don't. I am, a heart, a
>reduction firing kind of guy. When I see that green flame licking the sky
>I get that
>giggly wiggly dance going on inside me -- not quite dancing naked under the
>moon, but close.
>
>I'm stumped and open to any, and all, responses. I admit this Glaze Quest
>has been the hardest part of my education in ceramics but well worth it.
>I read
>somewhere that there are a limited number of shapes one can throw on the
>wheel, but surface treatment is where it's at.
>
>So much to learn, what fun it is.
>Jonathan in LA
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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