[Clayart] Olympic DD-12 kiln

[vpitelka at dtccom.net]

Hi Wayne - 
David Woof already asked if you have the six venturi burners or the power
burners on your DD-12.  That would be good to know, but either way, it is
usually no problem getting even reduction on a downdraft kiln managed
carefully.  It's a matter of maintaining a neutral or slightly oxidizing
atmosphere up to 1600F or so, and then a partial reduction up to maturation
temperature.  No need for heavier reduction at any time. 

 If your kiln is equipped with the venturi burners, don't mess with the air
shutters on the air-intake.  They should be opened just enough for a clean
flame (little or no orange/yellow) and then don't touch them again.  All
adjustment of atmosphere should be accomplished the gas valve(s) and the
damper.  

I know that the venturi burners on the DD-12 come up through the floor along
either edge, which is a good setup.  I do not know what the arrangement is
with the power burners.  I would hope they would be mounted at the rear
corners so the flame is directed forwards along the inside side walls.  With
power burners, you need to adjust the blower speed (or the air shutter on
the blower intake if so equipped) along with the gas valve(s) and the
damper.  

One of the most common mistake people make in attempting to initiate
reduction is closing down the air shutters on venturi burners, limiting
entry of primary air and producing a sleepy orange flame.  Such a flame is
only reducing in the places where it goes.  Once all the gas in that flame
burns, it is no longer reducing.  Without closing down the damper a bit to
increase back-pressure, what you get is streaming, where the flames and
reducing atmosphere are pulled directly towards the flue, and reduction is
achieved only along the flame's path.  

Instead, increasing back-pressure by closing the damper a bit will limit
entry of secondary air around the burner tips, causing incomplete combustion
of the fuel and producing the kiln atmosphere rich in carbon monoxide that
you need for even reduction.  Maintaining the right adjustment on the air
shutters produces a more turbulent flame that helps circulate that
atmosphere throughout the kiln.  

Go to my website and access the documents and handouts page and scroll down
to the section on kilns and firing.  You'll find a number of handouts about
firing different kilns.  There isn't one that matches what you have unless
you have the power burners.  But several of those handouts give good advice
on how to achieve even reduction.  

Good luck, and please feel free to elaborate on your firing protocol as
David Woof requested.
- Vince

Vince Pitelka
Potter, Writer, Teacher
Chapel Hill, NC
vpitelka at dtccom.net
www.vincepitelka.com 
https://chathamartistsguild.org/ 

From: Clayart <clayart-bounces at lists.clayartworld.com> on behalf of Wayne
Rives <wrives43 at gmail.com>
Sent: Wednesday, October 26, 2022 7:33 AM
To: clayart at lists.clayartworld.com <clayart at lists.clayartworld.com>
Subject: [Clayart] Olympic DD-12 kiln

I would like to chat with anyone using the DD-12 on propane. I've never been
able to get consistent reduction with this kiln.

Wayne Rives, Youngsville, NC

Sent from my iPad
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