cape1764@biddeford.com on fri 19 apr 96
Howdy all... Having a downdraft kiln myself I can't help my friend so She asked
if I could ask everyone at clayart. Here goes... Laurie has a 50 cu.ft updraft
kiln with forced air burners. She has to go to ^13 at the bottom in order to
get almost to ^9 at the top. She has a good reduction in the bottom half of
the kiln and the top is basically throw away area. When reducing she leaves the
air and gas pressure the same and pushes in the damper (as suggested by the
manufacturer). What can she do to help even out her firings? TIA Tracy at
Saltbox Pottery, Woolwich, Maine
Marvin Bartel on fri 19 apr 96
>----------------------------Original message----------------------------
>Howdy all... Having a downdraft kiln myself I can't help my friend so She asked
>if I could ask everyone at clayart. Here goes... Laurie has a 50 cu.ft updraft
>kiln with forced air burners. She has to go to ^13 at the bottom in order to
>get almost to ^9 at the top. She has a good reduction in the bottom half of
>the kiln and the top is basically throw away area. When reducing she
>leaves the
>air and gas pressure the same and pushes in the damper (as suggested by the
>manufacturer). What can she do to help even out her firings? TIA Tracy at
>Saltbox Pottery, Woolwich, Maine
Try making the bagwalls (bricks that baffle the flme in the kiln) higher.
* * * * * * Marvin Bartel * * * * * *
Art Dept., Goshen College
Goshen IN 46526
marvinpb@goshen.edu
phone 219-535-7592
fax 219-535-7660
http://www.goshen.edu
* * * * * * * * * * * * * * * * * * *
See Goshen College Alumnus
Dick Lehman on Ceramics Monthly Cover
* * * * * * * * * April, 1996 * * * * * * * * * *
Shrope/Ratcliffe on fri 19 apr 96
Marvin Bartel wrote:
>
> ----------------------------Original message----------------------------
> >----------------------------Original message----------------------------
> >Howdy all... Having a downdraft kiln myself I can't help my friend so She ask
> >if I could ask everyone at clayart. Here goes... Laurie has a 50 cu.ft updra
> >kiln with forced air burners. She has to go to ^13 at the bottom in order to
> >get almost to ^9 at the top. She has a good reduction in the bottom half of
> >the kiln and the top is basically throw away area. When reducing she
> >leaves the
> >air and gas pressure the same and pushes in the damper (as suggested by the
> >manufacturer). What can she do to help even out her firings? TIA Tracy at
> >Saltbox Pottery, Woolwich, Maine
>
> Try making the bagwalls (bricks that baffle the flme in the kiln) higher.
>
> * * * * * * Marvin Bartel * * * * * *Good idea! to increase the
also keep the damper slightly closed after body reduction, until you reach c8 on
the primary and secondary air a bit...A slower kiln is more even....you can even
gas pressure just a bit after c8. It may appear that the kiln has stalled, and i
have...for awhile, but it'll come back. From c8 to 10 may take 2 more hours. In
slower, even, slightly reducing kiln comes out more consistent. Good Luck, Peter
Vince Pitelka on sat 20 apr 96
Tracy -
The system Laurie has is comparable to that on the Alpine and Unique updraft
forced-air kilns, both of which are capable of even reduction top to bottom.
In general terms, to get heat to the top of an updraft you open the damper
further and to concentrate heat at the bottom you close it further. What
really helps is to be able to control oxidation/reduction as much at possible
at the source - the burners. No matter how accurate a rheostat you have on the
burner motors (I have never seen a really good one for those small motors), an
air shutter on the blower intake is a must for controlling atmosphere at the
source. Higher blower speeds, and therefore high turbulence, with the DAMPER
closed down quite far to initiate reduction tends to concentrate heat at the
bottom. But in terms of Laurie's problem, low blower speeds and/or the
air-shutter closed down further (low turbulence), with the damper open a little
will still give reduction but with more concentration of heat at the top. Heat
distribution during oxidation is simple - open damper = heat to top, close down
damper some with blowers up high = heat to bottom.
- Vince
Vince Pitelka - wkp0067@tntech.edu
Appalachian Center for Crafts - Tennessee Technological University
Smithville, TN
Donald Goldsobel on sat 20 apr 96
>----------------------------Original message----------------------------
>Howdy all... Having a downdraft kiln myself I can't help my friend so She asked
>if I could ask everyone at clayart. Here goes... Laurie has a 50 cu.ft updraft
>kiln with forced air burners. She has to go to ^13 at the bottom in order to
>get almost to ^9 at the top. She has a good reduction in the bottom half of
>the kiln and the top is basically throw away area. When reducing she
leaves the
>air and gas pressure the same and pushes in the damper (as suggested by the
>manufacturer). What can she do to help even out her firings? TIA Tracy at
>Saltbox Pottery, Woolwich, Maine
>
>I have found that the most effective way to even off a firing in an updraft
is to slow down the firing about 2 cones before maturity and adjust the
damper to regulate the upward movement of the heat. I don't know the number
of burners you have, but try retarding one or the other to see if it effects
the distribution of heat.
I hope this was of some help. Good luck.
art_selsor@vicuna.emcmt.edu on sat 20 apr 96
I fired Alpines at Carbondale, Ill. while in grad school. To get the
bottom even with the top (while also using damper to control) I raised
the "kiln shelf" bag wall structure up on little bits of kiln shelves
to get some direct heat into the bottom of the kiln. It worked. Fired
even without difficulty.
Marcia in Montana where we fire at 3000ft. with venturi burners!
Erin Hayes on wed 24 apr 96
Maybe this is silly, but it works - to get my ancient old Alpine to even
out and reduce well (despite its decrepit state), I put an old firebrick
on the top shelf right beneath the damper hole as a baffle.
It's not a very elegant solution, but it *does* keep the top shelf stuff
from being really pukey-looking. The kiln seems to be a little more
even, too, although it was never far off to begin with...
=============================================================================
Erin Hayes, Art and Humanities Instructor Office: (509) 575-2418
Yakima Valley Community College E-mail: ehayes@ctc.edu
PO Box 1647
Yakima, WA 98907 "Clay is Good."
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