Hank Murrow on wed 27 sep 00
Sylvia wrote;
>I've been trying to eliminate an ongoing blisters/pinhole problem.
> I've put draw rings of both these glazes in a load. The Reitz green was
>shiny, clear, and BLUE already at ^1 and stayed that way. It didn't
>develop the matt green until about 1850F on the way down. The rutile
>blue was also melted early smooth and tan (no blue whatsoever) until
>about 1650F on the cool down cycle when it turned blue. So my most
>recent thought is that the faults are related to atmosphere and are
>occurring on the cool down when the glazes are developing crystalline
>structure.
>Right now, I'm wondering if those who down fire rather then immediately
>clamming up the kiln notice any decrease in glaze faults.??
Dear Sylvia;
I too, fire the Reitz green over a porcelain body. However, I fire this and
several other glazes(including a copper yellow) in oxidation to C/10. I
reduce the body around C/010 to get whatever body/glaze interaction I can,
and then no back pressure or flame at the flue til shutdown. I damper the
kiln and let it cool to C/1 or so, starting it up again about 1/3 pressure,
and again in oxidation for 2-6 hours, then cool normally. The pinholes are
almost nonexistent fired this way,and the colors are spectacular. My draw
trials show that most of my glaze colors, whether reduction or oxidation,
are developing around 1500 to 1600F, during the cooling. With the Reitz
Green, I get an almost clear where it is thinnest, to cerulean blue, to
charcoal, to the mossy green the glaze is known for. BTW, you can leave the
GB out to better effect. You can see a picture of this and the Cu-yellow in
Ian Currie's new book, "Revealing Glazes"; which can be purchased by credit
card via the author's website: http://ian.currie.to/ . If you are
interested, I can send you pics at your eMail address.
Good Luck, and let us know how it turns out, Hank in Eugene
Mark Mondloch on wed 27 sep 00
I've been trying to eliminate an ongoing blisters/pinhole problem that I
have in my ^10 gas kiln firings with Reitz Green (a cobalt green)and my
rutile blue. I don't think it's a formulation problem. It seems to
occur in certain areas of the kiln (which changes from one firing to the
next). I've tried slowing the firing, soaking, changing reduction,
changing the stack.
I've put draw rings of both these glazes in a load. The Reitz green was
shiny, clear, and BLUE already at ^1 and stayed that way. It didn't
develop the matt green until about 1850F on the way down. The rutile
blue was also melted early smooth and tan (no blue whatsoever) until
about 1650F on the cool down cycle when it turned blue. So my most
recent thought is that the faults are related to atmosphere and are
occurring on the cool down when the glazes are developing crystalline
structure. Could that make any sense?
Right now, I'm wondering if those who down fire rather then immediately
clamming up the kiln notice any decrease in glaze faults.?? I don't have
problems with these glazes in my wood kiln (unless they're in a very
enclosed location). That kiln cools fairly slow because of the hard
brick mass but it's old and leaks like a sieve so there would be much
more air going through on the cool down. So the plan is that next gas
firing I will fire down for awhile (to below 1650F??) to maintain some
air movement through the load, but I'd really love to hear some input on
this.
Thanks,
Sylvia
--
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake, WI 53075
silvercreek@execpc.com
http://www.execpc.com/silvercreek
Mark Mondloch on thu 28 sep 00
Thanks for the reply Hank,
2-6 hr. is a pretty big range of time. Do you notice any difference at 2
hr. vs 6 hr.?
I assumed that the gerstley borate was in the Reitz green mostly to
suspend it in the bucket. Why do you feel it's better without and
doesn't it settle bad without it?
I was thinking of ordering that book and will get my butt in gear.
I will try your down-firing schedule next time that I fire (in about 2
weeks) and let you know what happens.
Thanks again,
Sylvia
Hank Murrow wrote:
>
> Dear Sylvia;
> I too, fire the Reitz green over a porcelain body. However, I fire this and
> several other glazes(including a copper yellow) in oxidation to C/10. I
> reduce the body around C/010 to get whatever body/glaze interaction I can,
> and then no back pressure or flame at the flue til shutdown. I damper the
> kiln and let it cool to C/1 or so, starting it up again about 1/3 pressure,
> and again in oxidation for 2-6 hours, then cool normally. The pinholes are
> almost nonexistent fired this way,and the colors are spectacular. My draw
> trials show that most of my glaze colors, whether reduction or oxidation,
> are developing around 1500 to 1600F, during the cooling. With the Reitz
> Green, I get an almost clear where it is thinnest, to cerulean blue, to
> charcoal, to the mossy green the glaze is known for. BTW, you can leave the
> GB out to better effect. You can see a picture of this and the Cu-yellow in
> Ian Currie's new book, "Revealing Glazes"; which can be purchased by credit
> card via the author's website: http://ian.currie.to/ . If you are
> interested, I can send you pics at your eMail address.
> Good Luck, and let us know how it turns out, Hank in Eugene
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
--
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake, WI 53075
silvercreek@execpc.com
http://www.execpc.com/silvercreek
Hank Murrow on thu 28 sep 00
>Thanks for the reply Hank,
>2-6 hr. is a pretty big range of time. Do you notice any difference at 2
>hr. vs 6 hr.?
***Yes, the effects vary proportionally. Longer time = deeper
color. i hasten to add that this holds true only for glazes which acheive
their color through re-crystallization in cooling. tenmokus, celadons,
copper reds, and chuns need not apply. Now Ohatas and Shaners! Look Out!
>I assumed that the gerstley borate was in the Reitz green mostly to
>suspend it in the bucket. Why do you feel it's better without and
>doesn't it settle bad without it?
***No settling problems yet; but i use vee-gum in all my glazes.
>I was thinking of ordering that book and will get my butt in gear.
***Truly great book.
>I will try your down-firing schedule next time that I fire (in about 2
>weeks) and let you know what happens.
>Thanks again,
>Sylvia
***Hey, no fear, as Ian says, Hank (who will love to hear)
Ron Roy on tue 3 oct 00
Hi Sylvia,
I'm betting you are using a fire clay body and it is not getting enough
oxygen during the bisque firing. Make sure you have a strictly oxidizing
atmosphere between 700C and 900C during you bisque cycle and don't go to
fast - say 100c per hour and test the atmosphere with some combustible -
like a splinter of wood or cardboard. If they flame in the kiln it means
there is excess oxygen - what you want - if not cut the gas down or open
your damper till you have an oxidizing atmosphere.
The real indication that the iron is being reduced - becoming a flux and
overfiring the body - when you refire the blisters are still there - and
maybe worse.
The worst cases of this result in black coring and bloating - check the
Hamer book for an excellent explanation.
RR
>I've been trying to eliminate an ongoing blisters/pinhole problem that I
>have in my ^10 gas kiln firings with Reitz Green (a cobalt green)and my
>rutile blue. I don't think it's a formulation problem. It seems to
>occur in certain areas of the kiln (which changes from one firing to the
>next). I've tried slowing the firing, soaking, changing reduction,
>changing the stack.
>
> I've put draw rings of both these glazes in a load. The Reitz green was
>shiny, clear, and BLUE already at ^1 and stayed that way. It didn't
>develop the matt green until about 1850F on the way down. The rutile
>blue was also melted early smooth and tan (no blue whatsoever) until
>about 1650F on the cool down cycle when it turned blue. So my most
>recent thought is that the faults are related to atmosphere and are
>occurring on the cool down when the glazes are developing crystalline
>structure. Could that make any sense?
>
>Right now, I'm wondering if those who down fire rather then immediately
>clamming up the kiln notice any decrease in glaze faults.?? I don't have
>problems with these glazes in my wood kiln (unless they're in a very
>enclosed location). That kiln cools fairly slow because of the hard
>brick mass but it's old and leaks like a sieve so there would be much
>more air going through on the cool down. So the plan is that next gas
>firing I will fire down for awhile (to below 1650F??) to maintain some
>air movement through the load, but I'd really love to hear some input on
>this.
>Thanks,
>Sylvia
>--
>Mark & Sylvia Mondloch
>Silver Creek Pottery & Forge
>W6725 Hwy 144
>Random Lake, WI 53075
>
>silvercreek@execpc.com
>http://www.execpc.com/silvercreek
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Mark Mondloch on tue 3 oct 00
Ron Roy wrote:
> I'm betting you are using a fire clay body and it is not getting enough
> oxygen during the bisque firing. Make sure you have a strictly oxidizing
> atmosphere between 700C and 900C during you bisque cycle and don't go to
> fast - say 100c per hour and test the atmosphere with some combustible -
> like a splinter of wood or cardboard. If they flame in the kiln it means
> there is excess oxygen - what you want - if not cut the gas down or open
> your damper till you have an oxidizing atmosphere.
Hi Ron,
I bisque sometimes in the electric and sometimes in the gas and haven't
noticed any difference. The electric is vented and the gas I run with
the damper full open and oxy probe indicating oxidation during that
period. I checked my recent bisque schedules and time wise I'm well
with-in your recommendation. No problems with black-core or bloating.
I have noticed that the pinhole problem is more prevalent with the Reitz
Green when I single fire it. There seems to be still some sulfur fumes
at the end of electric bisques (can't tell in the gas kiln). So I
thought perhaps sulfur may be a factor?
I've had much better luck refiring pieces in the electric(old Stoker
Kiln, semi hard castable) then in the gas kiln and I don't know what to
make of that. The pin holes smooth out and colors are deep. I figured
this may have a correlation to Hank's oxidation soak.
This is my clay body. I change proportions to favor the more coarse
materials (and add small amount of paper pulp) for larger scale tile and
wheel work.
50 Goldart
15 APGreen Fire clay (screened)
15 Cedar Heights Bonding Clay (screened)
13 Custer Spar
7 Flint
-----------
12 Kyanite 35m
8 Grog Calomo 60m
Comments on the recipe? I sure appreciate the input on this.
I realized that when I started to fire the little wood kiln years ago, I
just tried many glazes until I found ones that worked with the way I
happened to be firing. Now I have glazes I want to use and am trying to
adjust the firing so they work. I'm learning allot but sometimes it
makes my brain hurt. :)
Sylvia
>
> >I've been trying to eliminate an ongoing blisters/pinhole problem that I
> >have in my ^10 gas kiln firings with Reitz Green (a cobalt green)and my
> >rutile blue. I don't think it's a formulation problem. It seems to
> >occur in certain areas of the kiln (which changes from one firing to the
> >next). I've tried slowing the firing, soaking, changing reduction,
> >changing the stack.
> >
> > I've put draw rings of both these glazes in a load. The Reitz green was
> >shiny, clear, and BLUE already at ^1 and stayed that way. It didn't
> >develop the matt green until about 1850F on the way down. The rutile
> >blue was also melted early smooth and tan (no blue whatsoever) until
> >about 1650F on the cool down cycle when it turned blue. So my most
> >recent thought is that the faults are related to atmosphere and are
> >occurring on the cool down when the glazes are developing crystalline
> >structure. Could that make any sense?
> >
> >Right now, I'm wondering if those who down fire rather then immediately
> >clamming up the kiln notice any decrease in glaze faults.?? I don't have
> >problems with these glazes in my wood kiln (unless they're in a very
> >enclosed location). That kiln cools fairly slow because of the hard
> >brick mass but it's old and leaks like a sieve so there would be much
> >more air going through on the cool down. So the plan is that next gas
> >firing I will fire down for awhile (to below 1650F??) to maintain some
> >air movement through the load, but I'd really love to hear some input on
> >this.
> >Thanks,
> >Sylvia
> Ron Roy
> 93 Pegasus Trail
> Scarborough
> Ontario, Canada
> M1G 3N8
> Evenings 416-439-2621
> Fax 416-438-7849
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
--
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake, WI 53075
silvercreek@execpc.com
http://www.execpc.com/silvercreek
| |
|
