Norm Straker on mon 9 nov 98
Hey Folks,
Wondering if there are some ways to speed firing, cut the firing time??
Is there a way to bring the clay past the 100C degree mark without the
clay exploding!
Also, getting past the quartz inversion point??
I get the impression from some potters that they feel the longer the
firing, the "better" the product. Ridiculous right??
Just throwing out some ideas...
Thanks in advance! Norm! 8^o
___________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
or call Juno at (800) 654-JUNO [654-5866]
Brad Sondahl on tue 10 nov 98
-Is there a way to bring the clay past the 100C degree mark
-without the clay exploding!
If the pots are dry they will not explode. I dry pots on
shelves in the kiln room up near the ceiling before
bisqueing them, using waste heat from the kiln to eliminate
this problem.
-Also, getting past the quartz inversion point??
A valid question, but with an electric kiln it's hard to
push the heat in fast enough to generate cracks from that.
Although if cranked to high without time to adjust, uneven
heating can generate cracks.
-I get the impression from some potters that they feel the
longer
-the firing, the "better" the product. Ridiculous right??
The important part of glaze development generally occurs at
the high end. Many potters advocate a soaking period at or
near the top to improve glaze quality. I've depended on the
kiln sitter and been happy with what I've got.
My feeling is that 6-8 hours is appropriate for bisque (cone
05)
and 8-12 hours for glaze (cone 10), firing electrically.
Certainly a lot of energy is wasted by taking too long to
come to temperature.
--
Brad Sondahl
Sondahl homepage http://www.camasnet.com/~asondahl/
Brad's Index
http://www.camasnet.com/~asondahl/bradindex.html
Contributing to the potluck of the WWW
Kathi LeSueur on tue 10 nov 98
After over twenty years of cone 10 reduction firing I've come to the
conclusion that fast firing is not a good thing to strive for.
There was a time when I was proudly firing to cone 10 in eight hours. Some
glazes could take this fast fire. But I've found that if I want to keep glaze
problems to a minimum I have to fire for at least 12 hours. I slow the kiln
down so that the time between cone 05 and 10 is about 6 to seven hours. The
last hour of firing is extremely slow with a 45 minute soak after that.
This has virtually eliminated pinholing, cratering, etc.
Kathi LeSueur
Barney Adams on tue 10 nov 98
Speaking from the novice perspective and I'll defer to all the more
experienced potters, As I understand this point of going slow in the
firing the idea is that there is a temperature diffrence due to the
radiant tranference of heat from the outside of the pot to the inside>
(this is much more appropriate to electric as you can think of the
heat being transfer via line of sight from the elements. (I'm not
sure about a gas environment). Also the kiln shelves act as a heat sink
cause the bottom to be cooler than the top portion of the pot sitting
on it. The heat in the kiln is trying to equalize through out and when
held at a temp finds an average temp (this may vary by position in the
kiln, but within the area of a single pot the temp should for all intents
become even, I think). The slow increase allows this evening out, whereas
a rapid increase always has one part of a pot hotter than another part.
At least this is how I understand the slow as you go reasoning. It is'nt
that you cant go faster, but you want an even rise in temperature and a
slower rate helps insure this. My success rate in firings stands as witness
to the slow is safer (I wont say better).
Barney
> ----------------------------Original message----------------------------
> -Is there a way to bring the clay past the 100C degree mark
> -without the clay exploding!
> If the pots are dry they will not explode. I dry pots on
> shelves in the kiln room up near the ceiling before
> bisqueing them, using waste heat from the kiln to eliminate
> this problem.
>
> -Also, getting past the quartz inversion point??
>
> A valid question, but with an electric kiln it's hard to
> push the heat in fast enough to generate cracks from that.
> Although if cranked to high without time to adjust, uneven
> heating can generate cracks.
>
> -I get the impression from some potters that they feel the
> longer
> -the firing, the "better" the product. Ridiculous right??
>
> The important part of glaze development generally occurs at
> the high end. Many potters advocate a soaking period at or
> near the top to improve glaze quality. I've depended on the
> kiln sitter and been happy with what I've got.
> My feeling is that 6-8 hours is appropriate for bisque (cone
> 05)
> and 8-12 hours for glaze (cone 10), firing electrically.
> Certainly a lot of energy is wasted by taking too long to
> come to temperature.
> --
> Brad Sondahl
> Sondahl homepage http://www.camasnet.com/~asondahl/
> Brad's Index
> http://www.camasnet.com/~asondahl/bradindex.html
> Contributing to the potluck of the WWW
>
Stephen Mills on wed 11 nov 98
In message , Norm Straker writes
>----------------------------Original message----------------------------
>Hey Folks,
>
>Wondering if there are some ways to speed firing, cut the firing time??
>
>Is there a way to bring the clay past the 100C degree mark without the
>clay exploding!
>
>Also, getting past the quartz inversion point??
>
>I get the impression from some potters that they feel the longer the
>firing, the "better" the product. Ridiculous right??
>
>Just throwing out some ideas...
>
>Thanks in advance! Norm! 8^o
>
>___________________________________________________________________
I don't agree,
Fast firing produces good glazes. Slow firing produces better glazes,
you get better dispersion of the materials, rather like putting on a
heavy coat and getting comfortable in it. I've done both, I now only do
the latter.
Steve
Bath
UK
--
Steve Mills
Bath
UK
home e-mail: stevemills@mudslinger.demon.co.uk
work e-mail: stevemills@bathpotters.demon.co.uk
own website: http://www.mudslinger.demon.co.uk
BPS website: http://www.bathpotters.demon.co.uk
Ron Roy on wed 11 nov 98
It is my experience that longer firings tend to solve problems and shorter
firing tend to produce more. If you have a controller then there are
certain stages when fast firing is OK but most of us simply want to turn it
on and let er go with a minimum of care.
The idea that slow firing is better - for us anyway - is not ridiculous -
it allows for a better clay/glaze bond, less glaze flaws, more even
firings, less wear and tear on kilns and furniture and less built in
stress.
If you want to fast fire you had better have some insight into the
technical aspects of your clays and glazes and how to apply that
information.
RR
>----------------------------Original message----------------------------
>Hey Folks,
>
>Wondering if there are some ways to speed firing, cut the firing time??
>
>Is there a way to bring the clay past the 100C degree mark without the
>clay exploding!
>
>Also, getting past the quartz inversion point??
>
>I get the impression from some potters that they feel the longer the
>firing, the "better" the product. Ridiculous right??
>
>Just throwing out some ideas...
>
>Thanks in advance! Norm! 8^o
>
>___________________________________________________________________
>You don't need to buy Internet access to use free Internet e-mail.
>Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
>or call Juno at (800) 654-JUNO [654-5866]
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Fraser on thu 12 nov 98
Now all I do is fast fire (2-3 hours for cone 7/8). Some of my glazes did
have pin hole problems in the
past, when I used an electric kiln. Over the past 1 1/2 years I've
developed a
dozen or so glazes and none have acted up. I was not so lucky when firing
in an electric
kiln.
I speculate the carbon in the atmosphere has positive influence on the
glaze.
The melt probably happens sooner, the glaze(s) become less viscous and a
more
efficient fluxing action takes place all around the glaze - not just in and
under the
glaze.
Can't remember but there is a rather thick book out there on nothing but
Copper
Red. In this work the author is always emphasizing the importance of the
atmosphere
around the surface of the (molten) glaze, for fluxing, and ion transfer
esp. with regard
to copper reds.
Not a chemist - just guessing at a possible theory; but I know it can be
done.
Fraser Forsythe
.....in a very windy storm
Reid Harvey on fri 13 nov 98
I am reminded of fast firing techniques I heard about, used in Italy for
a fast firing cycle. The secret of their success is a high talc claybody
that contains no clay. Firing in a tunnel kiln it takes only one hour
from the time the tile enters the kiln to the time it goes into the box,
packed for shipment.
| |
|
