[Clayart] Olympic DD-12 kiln

[William Schran]

I had an Olympic updraft kiln for a period of time and the burners
that came with the kiln appear to be the same type burners - a primary
air disk on bottom part of the burner and the top portion a straight
pipe. Fired this kiln with propane and always had issues with back
burning or too much reduction. I finally switched out to true venturi
burners from Ward Burners and that solved most all issues.
I totally agree with what Vince wrote about having primary air disks
set at a certain opening (on the Geil kiln I fired where I taught, the
primary air was open the thickness of 2 wood popsicle sticks) and
never adjusted. Only adjusted gas pressure (often 1/2 recommended
pressure) and adjustments to damper.

William Schranwschran at twc.com703-505-1617

	-----------------------------------------From: vpitelka at dtccom.net
To: "Clayart international pottery discussion forum"
Cc: 
Sent: Thursday October 27 2022 10:40:34AM
Subject: Re: [Clayart] Olympic DD-12 kiln

 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/ [1]

 From: Clayart  on behalf of Wayne
 Rives 
 Sent: Wednesday, October 26, 2022 7:33 AM
 To: 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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Links:
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[1] https://chathamartistsguild.org/

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