C Sullivan on wed 15 sep 10
Hola there Folks
The bottom shelf of my gas kiln, at maximum temps, runs several degrees
under the middle and top shelves.
I have some cone 5-6 Coyotte glazes but they won't mature on the bottom
shelf .........
My question is:
If i add some gherstley borate and some lithium to the coyotte glazes, will
that bring the maturing temps down to approx cone 4 ???
Before this, i only used the middle shelf but would like to start firing
more pieces in one firing.
Any ideas ???
Thank you
Chae
Pottery by John on thu 16 sep 10
Hello Chae, haven't seen you posting in a while.
Since heat work is a combination of temperature and time, you might try
holding at temperature longer to even out the kiln. I fire Coyote to Cone
6, but they do mature at Cone 5, so a few degrees less on the lower shelf
may work with a bit more time.
If I was a gas guru I might ask some good questions and give you some good
answers on how to even out top and bottom. As I am not, the archives have =
a
lot of that kind of advice therein.
Reformulating a commercial glaze without knowing what's in it would not be
my first approach. I added some Mason Titanium Yellow stain to a commercia=
l
clear crackle raku glaze and got a (nice) green. At least I liked the
color.
Good luck with it.
John Lowes
Sandy Springs, Georgia
http://wynhillpottery.weebly.com/
William & Susan Schran User on thu 16 sep 10
On 9/15/10 6:34 PM, "C Sullivan" wrote:
> Hola there Folks
> The bottom shelf of my gas kiln, at maximum temps, runs several degrees
> under the middle and top shelves.
> I have some cone 5-6 Coyotte glazes but they won't mature on the bottom
> shelf .........
> My question is:
> If i add some gherstley borate and some lithium to the coyotte glazes, wi=
ll
> that bring the maturing temps down to approx cone 4 ???
> Before this, i only used the middle shelf but would like to start firing
> more pieces in one firing.
> Any ideas ???
Perhaps before altering the glazes, you would explain type of kiln, firing
schedule, etc and what measures you have taken to try and even out the
temperature in the kiln.
Just a few % of lithium would bring down melt temperature.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Michael Wendt on sun 19 sep 10
Chae,
I would never mess with the glaze first but try to even out
the kiln.
If your clay is formulated to fire cone six and you only
fire it cone five, it may not perform properly in use.
I found one of the easiest ways to even out a firing that
runs cold on the bottom is to increase the height of the
bottom layer. Basically, kiln shelves act like radiation
barriers in a kiln, slowing heat transfer in the vertical
direction.
Raising the height of the layer brings the top parts of the
pots on that layer into a more direct line with the hotter
middle part of the kiln. They then conduct more heat to the
bottom as well.
To still get the maximum load possible, I made small trumpet
shaped setters of different diameters to accommodate various
pot foot sizes. The bottom of the riser is 2" in diameter
since that is the width of my kiln posts. Depending on the
shapes of the pots, I alternate with tall narrow pots on the
bottom shelves and lower wider pots set on kiln posts with
the trumpet shaped "jacks" supporting the actual pot foot
above them at the intersections. This also prevents warping
since the trumpets are very true and don't warp ( they're
made of 50% Helmer Kaolin and 50% Alumina, they work
great!).
I do the same thing on the top of the kiln since it always
tended to run cooler too.
Now I can get the same cone all the way from bottom to top
very easily. I can actually get way more work in the kiln
this way with far fewer kiln shelves.
It also increased fuel economy.
Now a 12 cubic foot load worth $2000 on average costs
$22.00/load. We tracked the loads per month this summer and
averaged them with the gas bill since they are the only
thing using gas in the summer.
Regards,
Michael Wendt
Hola there Folks
The bottom shelf of my gas kiln, at maximum temps, runs
several degrees
under the middle and top shelves.
I have some cone 5-6 Coyotte glazes but they won't mature on
the bottom
shelf .........
My question is:
If i add some gherstley borate and some lithium to the
coyotte glazes, will
that bring the maturing temps down to approx cone 4 ???
Before this, i only used the middle shelf but would like to
start firing
more pieces in one firing.
Any ideas ???
Thank you
Chae
Lee Love on mon 20 sep 10
Chae,
You are on the right track. It is how potters have traditionally
dealt with uneven kilns! Using them to their greatest potential!
It is called, "Paying attention to your processes and materials and
responding to them." As MacKenzie told a visitor, "An even kiln
ain't worth a damn!" I got three different looks out of my kiln
in Mashiko. I like the variety.
You might look at Linda Arbuckle's cone 3 glazes in her
handout. There are some great glazes in it.
--=3D20
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
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