[Clayart] 30+ year old Geil downfdraft kiln - firing help

[Donn Buchfinck via Clayart]

I pulled out an old Geil 12 cf downdraft kiln from storage.
It's the older kind with the cast iron burners.
I set it up and I have fired it twice and I get overfiring on the bottom
and under fired on the top.

The kiln stacks 2 12x24" shelves 36 " high.
ithas 6 MR 750 burners on it.

At three inches of natural gas the bottom 9 was down and not even 7 on
top.
It's just frying the bottom.

Any ideas?
I fired the newer Geil versions and they fired like a dream.
I am eyeing a new Geil Fiber but at $40K its a bit much.

As I fired the only way to get the top cones to move was to have the top
peep out. But each time I caught it too late.

I understand why there was a major redesign for the kilns.
Any and all ideas are greatly appreciated.

So I will try again.

This kiln has baffled me for years. Salt kilns, Soda, wood, downdraft
updraft, I seem to understand, but this kiln laughs at me. :-|

Thanks,
Donn Buchfinck
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[David Woof via Clayart]

Donn,
The kiln is trying to tell you what it needs, and it gave you a clue when you left the top peep open.
As with many other posts and discussions..... Controlled but Adequate Circulation through-out kiln is the key. Heat naturally rises. What can you do you are not doing to work with that?
Did you stagger the shelves as you built the setting? Are you stacking too tight mid to top loading of setting? Densely stacked pots can act as a baffle, and bigger/thicker pots take longer to absorb the heat and reach desired fired temp in contrast with other regions in the kiln.

With your background of firing experience you know all you need to know! Sometimes we just to have to let go of the tight mental/emotional grip we have on the problem, sit back ,relax, let thoughts wander as you connect the dots in different configurations and let what you need come to mind. Fishing or whittling can help this process.

Misneach,
David Woof..........................................................

________________________________
From: Clayart <clayart...@lists.clayartforum.com> on behalf of Donn Buchfinck via Clayart <cla...@lists.clayartforum.com>
Sent: Thursday, November 20, 2025 7:06 PM
To: cla...@lists.clayartforum.com <cla...@lists.clayartforum.com>
Cc: Donn Buchfinck <donn.bu...@gmail.com>
Subject: [Clayart] 30+ year old Geil downfdraft kiln - firing help

URL: <https://lists.clayartforum.com/pipermail/clayart/attachments/20251121/f77dcd57/attachment.htm>

[d jungle via Clayart]

Donn, I assume the 6 burners are positioned at the bottom, 3 on each side
pointing up. I can only imagine that the draw from the chimney/stack is at
the bottom and pulling the flames and heat towards it before the flame/heat
has a chance to travel up in the top area.
I would experiment with putting the damper in to reduce the draw of the
chimney or use a passive damper to achieve the same effect. This may
create more reduction so you'll have to adjust the primary/secondary air
and/or gas pressure to get it just right.
My 2 cents,
Good luck,
from another Don

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