Fara Shimbo on tue 13 may 03
Hi, Folks,
On the subject of crystalline firings and kilns, here are
my thoughts and observations over the last nine years.
Feel free to thoroughly trash them...
In my electric kilns, I get about 20-30 firings to ^9,
with or without ITC. The only difference I've noticed
in whether I use ITC or not is that when I change the
elements, the ITC ones can be rolled up and put back in
their original bags. The problem with crystalline firing
is, I think, the long soak periods for growing the
crystals. Because of this, in my view, each crystalline
fire can be considered one and a half normal fires. I was
told by one of the salesmen at the local Laguna place
(before it closed) that you can only expect about 40 ^9 ^10
firings out of a set of elements in any case; so twenty-five
firings gives you just about those 40 firings you would normally
expect.
I've only once changed elements because of an element
breaking. It broke at a spot where something exploded and
glaze melted onto it. I change elements mostly because
the last hundred degrees C is going too slowly and I'm not
getting crystals. I'm sure the elements I take out are
just fine for any other kind of firing.
My major problem with elements is that changing them is a
task so mind-numbing and aggravating that it's right up there
with root canals amongst things I'd rather not do. It's also
very expensive -- I was spending about US$600 a year for
new elements.
SO.... I went out and got an Olympic Torchbearer propane
kiln from BigCeramicStore. I love this thing. I've named
it Norbert. It goes to ^10 in four hours if I let it (now
that I finally got the propane place to give me the right
propane set up for it). Been getting some really spectacular
results with it, including copper reds and peach blooms and
this really astouding true emerald green. I'd recommend a
gas kiln to anyone who can have one, I realize that zoning
and covenant restrictions apply.
AND I DON'T HAVE TO CHANGE THE ELEMENTS, which has me
bouncing all over with joy!
And that's my diatribe on elements. Feh!
Fa
--
===========================================================
Fara Shimbo, Master Crystalliere, Certified Public Nuisance
-----------------------------------------------------------
Shimbo Pottery, P.O. Box 41, Hygiene, Colorado 80533 USA
720.272.0442 7AM to 2 PM, Mountain Time
www.crystalline-ceramics.info www.shimbopottery.com
Silly Science Fiction: http://klysadel.net
===========================================================
Fraser Forsythe on wed 14 may 03
Hi Fara.
Thanks for your comments.
I have been firing to cone 6 in a fibre kiln for
several years. The cones are bending in less than 3
hours. I use a venturi propane torch rated at 300,000
btu. Next time I'll get one rated at 500,000. Once the
water is out I blast it - full tilt. The pots are fine
as long as the cool down is at a normal slow pace. So
far this kiln serves to fire raku and cone 6 reduction
techniques.
I've recently been experimenting with crystalline
glazes in an electric kiln and have had lots of
success. I fire to cone 6 and soak for two hours after
letting the temp. drop 220f. I set the controller to
rise at 400f per hour. Takes 8 hours to put the cone
over, 10 minutes to drop temps, and 2 hours to soak.
Like the fibre kiln I reduce the amount of furniture
where possible. I only fire with one shelf about 2/3
up the kiln.
After reading your comments I'm going to try the same
thing in my gas kiln. In fact it sounds like my kiln
is probably ideal for crystalline because I can fire
so fast. I have a couple of questions for you:
1. do you find a big difference in cost between
electric and gas firing crystalline?
2. do you follow regular reduction patterns - say in
achieving a copper red effect when firing crystalline.
2a. would you hold the soak in a neutral or oxidizing
flame?
I'll probably experiment with the firing cycle but
thought I'd ask anyway.
thanks.
Fraser
=====
Fraser Forsythe
fraser@glazeexchange.com
Guelph,Canada
______________________________________________________________________
Post your free ad now! http://personals.yahoo.ca
Fara Shimbo on thu 15 may 03
Hi, Fraser,
Fraser Forsythe wrote:
> After reading your comments I'm going to try the same
> thing in my gas kiln.
Heck, don't take my word for anything, I'm new to this
whole gas-kiln thing myself. (Before I got this one
I hadn't used a gas kiln in forty years.)
> In fact it sounds like my kiln
> is probably ideal for crystalline because I can fire
> so fast. I have a couple of questions for you:
> 1. do you find a big difference in cost between
> electric and gas firing crystalline?
I really can't say. My gas kiln is a lot bigger than
my electrics. Last year the price of electricity
quadrupled (!) around here, and I think it costs me
about $13.00 per firing for the Skutt 818s. In the
gas kiln I seem to be using about 18-20 gallons of
propane at about $1.30 per gallon, but since the kiln
is at least twice as big, it probably works out to about
the same thing.
> 2. do you follow regular reduction patterns - say in
> achieving a copper red effect when firing crystalline.
Well, I've yet to get anything that's entirely copper
red. But what I do, for the heck of it, is begin reducing
when the glaze begins to melt, and carry on reducing
until the glaze is completely melted, then go up in
oxidation to the end.
Just an aside, because the kiln has a big top port,
I can hold up a piece of polished sheet steel and
watch the pieces as they fire. What I've been seeing
can cause you heart failure. As the glaze melts it
crawls something fierce, and you'd never believe it
could possibly melt out again and cover the piece.
But it always does. Very amazing.
> 2a. would you hold the soak in a neutral or oxidizing
> flame?
Either will do. I haven't tried soaking in reduction.
It's too big a kiln for that kind of test for me...
Hope this helps, please feel free to ignore all advice,
Fa
--
===========================================================
Fara Shimbo, Master Crystalliere, Certified Public Nuisance
-----------------------------------------------------------
Shimbo Pottery, P.O. Box 41, Hygiene, Colorado 80533 USA
720.272.0442 7AM to 2 PM, Mountain Time
www.crystalline-ceramics.info www.shimbopottery.com
Silly Science Fiction: http://klysadel.net
===========================================================
Jocelyn McAuley on thu 15 may 03
I decided to post my private reply to the list, since I just saw how
different my and Fa's firing styles are. Fara's style is interesting
given the discussion on losing zinc in reduction.
____________________________________________
Hi Fraser
Reduction with crystal glazes is crucially different than traditional
reduction glazes. As noted many times on this list- reduction at high
temperatures makes your zinc go bye-bye. So, to get around this, a typical
(if we can use that word!) crystalline reduction firing involves reduction
on the way down.
In my reduction fires I fire my gas kiln with the same schedule I would
program my electric... but after doing all the cooling holds when your
kiln is at 1500F, fire it back up and put it in reduction. I've had
success holding reduction anywhere from 15min-45min.
*I don't take it back up to the gowing crystal temps- just reduce once it
has cooled to 1500F and then let it cool naturally.
An alternative to this, that I use the most, is to fire my crystal pieces
in my electric kiln to ensure no reduction for one thing... and because
its easier time wise. Then I detach bases, grind down, and then fire
these "successfull" pieces to 1500F in the gas kiln and reduce at 1500F.
Good luck and have fun
Jocelyn
--
Jocelyn McAuley ><<'> jocie@worlddomination.net
Eugene, Oregon http://www.ceramicism.com
Fabienne Micheline Cassman on fri 16 may 03
My apologies if this was already mentioned. I don't have much time to read lately but figure this may be of interest.
There is an article on this subject. What you can extrapolate from it is when to do the reduction which is what I recal matters since reduction inhibits crystalline growth, I suspect timing is everything.
Ceramics Monthly, pp 35-7, March 1991
Crystal Glazes in Reduction! by Thomas S. Carroll
This article describes how the author developed a procedure to produce reduced crystalline glazes in an electric kiln. Crystalline glaze bases used for this type of firing are supplied.
Happy testing!
Fabienne
--
Fabienne Cassman http://www.milkywayceramics.com/
WARNING: I cannot be held responsible for the above
because my cats have apparently learned to type.
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