Lois Ruben Aronow on mon 3 dec 01
I REALLY look forward to Ron & Jon's book, and have already ordered my
copy. Ron, do you reveal any secrets to achieving a REALLY GOOD
tenmoku at cone 6? Like YOUR tenmoku? her heh....the one glaze
that's baffled me at cone 6.....
I'm going to ask this at the risk of sounding stupid. There has been
alot of talk about "controlled cooling" and "slow cooling". I do know
that the rate of cooling can drastically affect the glaze. BUT -- how
to achieve this cooling rate? I assume it's more than letting the
kiln turn off and letting it cool with the plugs in. Does it
involving ramping down?=20
My Skutt manual (yes, I have a computer controller) gives a ramp/hold
example of "controlled cooling". Basically, it involves letting the
kiln cool, and then soaking for 30 mins at a lower temp. Maybe I have
just answered my own question.
After the christmas crush I plan on doing some experimenting, and I
this cooling thing will be one of my projects. That, and finding a ^6
Tenmoku........
Marianne Lombardo on mon 3 dec 01
Lois,
When I began firing ^6 glazes, I had a lot of problems with pinholing and
craters, etc. I learned to bisque slower, which helped. Then John
Hesselbert suggested slower cooling. I believe he cools at 150F/hour from
1900F down to 1500F. I tried it, and it worked. I don't have a kiln
controller. All I have are on/off switches for each element, so it's taken
a while to figure out a pattern that worked with my kiln.
I've been playing around with different cooling rates. The last cooling I
did a bit different to experiment. I held it at 2220F for about 20 min,
then let it drop naturally to 2100F
which I think took about 45 minutes. Then by turning some switches back on
and it took 4-1/2 hours to cool to 1700F. That was too slow (about
90F/hour) for some of my glazes. I had a few puddles. But I did have one
absolute gem! It was worth the puddles to get this gem out of the kiln.
But I do not recommend this slow cooling, better stick with John's cooling
rate for more consistent results with the majority of glazes.
For me, it doesn't do anything for glazes like Rosenrot. They come out
mauve.
I am hoping that John and Ron's new book will get into more about this
subject.
> alot of talk about "controlled cooling" and "slow cooling". I do know
> that the rate of cooling can drastically affect the glaze. BUT -- how
> to achieve this cooling rate? I assume it's more than letting the
Marianne
Lexxy on mon 3 dec 01
If someone knows how to do slow cooling with the Skutt auto sitter would
they please post the method. I'm pretty sure that's just what I need too...
Lexxey
Please check out my website at: http://www.flummoxed.org/lexxey/index.htm
-
When I began firing ^6 glazes, I had a lot of problems with pinholing and
craters, etc. I learned to bisque slower, which helped. Then John
Hesselbert suggested slower cooling. I believe he cools at 150F/hour from
1900F down to 1500F. I tried it, and it worked. I don't have a kiln
controller. All I have are on/off switches for each element, so it's taken
a while to figure out a pattern that worked with my kiln.
I
Marianne
Lorraine Pierce on tue 4 dec 01
Hi Marianne... Can you be more exact about how you manipulate your cooling
cycle with the three switches/ which electric kiln you have, etc. The info
could really help the many claybuds without controllers. Which pyrometer
have you found best, and how do you use yours? thanks, Lori in New
Port Richey, Fl.
Jeff Lawrence on tue 4 dec 01
Lexxey was wondering about controlled cooling with her Skutt electric
kiln with computer controller.
Hi Lexxey,
I very distinctly remember when an employee lost the manual for my new
computer controlled Skutt. I stood on hold with the dealer, gnashing my
teeth and staring at the kiln when I suddenly realized I was staring at
instructions printed on the face plate. Furtively, I hung up...
As an example you can use to understand the process, here's a program I used
for a crystalline firing to cone 6, with a slow ramp of 50C/hour to 500C,
holding that temp for 1 hour (I was single firing and this helped), normal
temperature rise of 100C/hour to 1200C, soak there for 15 minutes, cool at
150C/hour to 1000 and hold for 5 hours, then cool normally. This is more
complicated than simple cooling, but it might help illustrate the simpler
case. Replace these values with your appropriate temps, rates of temp change
and hold times.
Press "Ramp/Hold" and then answer the following questions it asks (Stuff you
enter is spaced over to the right below):
User: 1
(pick any number you like from 1 to ??)
Segments: 3
(I forget how many stages are possible, might be 7 or 9)
Ramp 1 rate of temp change: 50C
Ramp 1 target temperature: 500C
Ramp 1 Hold time: 1:00 hours
Ramp 2 rate of temp change: 100C
Ramp 2 target temperature: 1200C
Ramp 2 hold time: 0:15 hours
Ramp 3 rate of temp change: 150C
Ramp 3 target temperature: 1000C
Ramp 3 hold time: 5:00 hours
It will also ask you for time to delay before starting the firing and an
alarm temperature (I forget the order). Select 0:00 delay if you want to
start right away. Select 9999 for alarm to keep it from going off at all.
Press "Review" when you've entered everything to make sure all the numbers
are what you had in mind.
Press "Start" when everything is entered just the way you want it.
Once it clicks it is a great system. I am personally a huge fan of the
possibilities of computer control of kilns, and am sure you will become one
as well once you get into it. If this is all unclear, check out the
controller face plate! ;->
Jeff Lawrence
jml@cybermesa.com
Marianne Lombardo on tue 4 dec 01
> Hi Marianne... Can you be more exact about how you manipulate your cooling
> cycle with the three switches/ which electric kiln you have, etc. The
info
> could really help the many claybuds without controllers. Which pyrometer
Not really... With the two add-on collars for more height, my kiln has 5
switches. It's a very old kiln, but in good shape. I have to literally sit
beside the kiln at that point and trying turning off maybe two switches,
perhaps bottom and top, and watch the temp on the pyrometer. If it starts
cooling too fast, I flip a switch back on. Eventually I usually reach the
point where I can leave switch 1, 3 and 5 on and leave it for a few minutes.
Lots of flipping switches and watching the temp. Usually I bring some other
work into the kiln room to work on while I "babysit".
I think my pyrometer is a Bartlett brand. I have nothing to compare as it
is the only one I've used. I bought it at Tuckers.
Marianne Lombardo
Peterborough, Ontario, Canada
Ron Roy on wed 5 dec 01
Hi Lois,
My Tenmoku is a reduction glaze - I don't think you can ever get that kind
of glaze at cone 6 oxidation - but if you are thinking of glazes that break
on any raised decoration and on edges - well that is possible - take a look
at the glazes on our web site - there are some interesting examples of such
glazes.
There are many reasons to slow cool and the it depends what you want to
happen that determines when.
For instance if it's pin holing due to an underfired glaze - instead of
reformulating for more melt you might just slow cool for the first 50
degrees - say 2 hours. I would prefer to reformulate for more melt but if
that lead to crazing - then the slower cool would be an answer.
The reason most potters would want to slow cool is to give some crystals
time to form or true mattes to develop. That means fast (normal) cool for
200 C then slow down for 200C. All glazes are going to respond in different
ways to this kind of heat treatment and the ideal would be to do a number
of experimental firings with different cycles.
Just make up enough test tiles to apply all your glazes to - times the
number of experiments you want to try. 10 glaze - 5 firings = 50 tiles of
each clay you use.
Load each kiln in such a way as to simulate a normal firing - extra shelves
and posts for instance.
Try slowing down 50C per hour from 1000C to 900C, 1000C to 800C, 900C to
700C - 800C to 700C - like that.
I predict you will see many "new" glazes - many of which you will find much
more interesting than those you are working with now.
Then write an article for a magazine or post the results to ClayArt - RR
>I'm going to ask this at the risk of sounding stupid. There has been
>alot of talk about "controlled cooling" and "slow cooling". I do know
>that the rate of cooling can drastically affect the glaze. BUT -- how
>to achieve this cooling rate? I assume it's more than letting the
>kiln turn off and letting it cool with the plugs in. Does it
>involving ramping down?
>
>My Skutt manual (yes, I have a computer controller) gives a ramp/hold
>example of "controlled cooling". Basically, it involves letting the
>kiln cool, and then soaking for 30 mins at a lower temp. Maybe I have
>just answered my own question.
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Lois Ruben Aronow on wed 5 dec 01
On Wed, 5 Dec 2001 00:25:51 -0400, you wrote:
>Hi Lois,
>
>My Tenmoku is a reduction glaze - I don't think you can ever get that =
kind
>of glaze at cone 6 oxidation - but if you are thinking of glazes that =
break
>on any raised decoration and on edges - well that is possible - take a =
look
>at the glazes on our web site - there are some interesting examples of =
such
>glazes.
I know it's reduction, but it's my fantasy glaze....... a girl can
dream, can't she? It's oh-so-beautiful.
Lois Ruben Aronow on wed 5 dec 01
>Try slowing down 50C per hour from 1000C to 900C, 1000C to 800C, 900C to
>700C - 800C to 700C - like that.
>
>I predict you will see many "new" glazes - many of which you will find =
much
>more interesting than those you are working with now.
>
>Then write an article for a magazine or post the results to ClayArt - RR
>
>
I will indeed. This is my project for the new year. I want to work
with controlled cooling and do a little experimenting with crystals.
Call me a masochist.
Ironically, all this comes on the heels of an *extremely*
disappointing firing I unloaded yesterday. All of my plates slumped
and stuck to the kiln shelves. Today will be spent scraping. And
scraping. And scraping. Stuff I thought would be nice was
uninteresting, at best. Sigh. I know it happens to everyone, and I
know that, with Murphy's law and all, that it is most likely to happen
5 days before the annual Xmas sale, but boy, am i DEPRESSED.
I came home yesterday devising ways of selling all my equipment and
getting a "real" job. =20
It's mainly disappointing because I spent A LOT of time being very
careful and thoughtful with my work, hoping to be inching ever closer
to a satisfying group of work. =20
Back to the old drawing board. Or wedging board, as the case may be.
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