[Clayart] Past clayart archives

[Donn Buchfinck via Clayart]

Hi,
Where can one access the old questions and replies for cc clayart?

Thanks

Donn Buchfinck
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[Robert D. Hill via Clayart]

Hello again Clayart
Long time member, mostly lurker.

Recently retired my larger soda kiln which needed major refurbishing and was too large for my current production.
Utilizing as much of the soda kiln bricks and steel structure and with the addition of other used bricks form a retiring potter I have constructed a small downdraft IFB brick kiln based loosely on the Kurt Wild plans from Mels fantastic kiln book. Slightly smaller interior space and with a sprung arch instead of flat top.

Interior size is 31 1/2" W - 29" Deep - 32" H. 9" thick walls and arch. Shelves are 10" X 20" and 12" X 20".
2 - MR 750 natural draft burners purchased from Ward burners about 10 yrs ago. Rated for about 75000 btu at 11" WC.
I am firing with propane and have maximum 15" WC pressure available, (about 1/2 lb. pressure)
Burner ports are coming in from the back of the kiln, either side of the brick chimney. Ports are 4" W X 4 1/2" Tall. Exit flue is 7" W X 4 1/2" tall. Chimney was existing and is 16' tall with 9" X 9' inside dimension, constructed from mortared hard brick.. I do have 2 passive damper openings in the chimney to help slow down the draft as the flue heats up and for when it is a high pressure/breezy day.

The reason I am giving all of the technical specs is that I am hoping for any advice and suggestions from all of you. I previously fired my large downdraft soda kiln with power burners and wondering how to control proper reduction atmosphere and even out the temperature through out the new kiln using the natural draft burners..

I have completed 1 firing to bisque ^08 and 1 glaze firing to ^6. ^6 in reduction is my goal and I did reach ^6 in about 12 hours.
Kiln was fired with the bottom shelf 2" off the floor of the kiln.
^7 was reached at front bottom, ^6 middle front, ^5 starting to bend top front. ^6 bending at back bottom, ^5 back middle, ^5 softening at back top. Started reduction by closing down the damper at^08 with 6-8"orange licking flame at top and middle peeps. Flame at peeps seemed to be smokey and with very little back pressure compared to firing with my previous power burner system. Results from the completed firing seems to suggest very little to no clay body or glaze reduction.

Any suggestions on controlling the air and gas mixture with these MR 750 burners for proper oxidation and heat rise and alternatively, for proper reduction without wasting fuel etc. Also a faster firing would be preferable.
Also, thoughts on getting the kiln temps to even out. I will be adding a target brick in the flameways for the next firing. (any suggestions on target brick size and location?)
Any thoughts on burner port, Flue exit and chimney? I realize the chimney size and height is overly large but am hoping to use it as it is existing and is the required height to exit the kiln shed roof.

I will take any and all advice from the group and truly appreciate all the knowledge I have gained over the last 25 years I have been on Clayart. If more specifics are needed let me know.
Thanks in advance.

Dan Hill
Hill Pottery
www.hillpottery.com

[ronroy--- via Clayart]

I just found this reference to the Glick article on his back problems

http://www.plumtreepottery.com/articles/


Ron Roy
ron...@ca.inter.net
Web page ronroy.net

[William Schran via Clayart]

I used this article years ago when switching form seated throwing to
stand up throwing.I made a lower back & butt cushioned support that
Ican press back into to brace and stabilize my torso while centering
and throwing.Made the switch in 2013 after surgery to lower back due
to spinal stenosis.
Bill

William Schran...@twc.com703-505-1617

-----------------------------------------From: "ronroy--- via
Clayart"
To: "Clayart international pottery discussion forum"
Cc: ron...@ca.inter.net
Sent: Friday November 14 2025 2:31:51PM
Subject: [Clayart] back problems

I just found this reference to the Glick article on his back problems

http://www.plumtreepottery.com/articles/
/>

Ron Roy
ron...@ca.inter.net
Web page ronroy.net

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[ronroy--- via Clayart]

Hi Dan,

I fired with atmospheric burners - that would be well over 1000
firings from where I am now and in Toronto..

Best advice I ever got was to direct flame to where you need reduction
and and heat.

I would use cones everywhere till you get what you want and I think
you are doing that.

If you think there is too much air coming in around the burners you
can use pieces of brick to cut down the secondary air.

Sounds like you need to direct some flame up.

6 to 8 inches seems like a lot of spy hole flame at the top. As you
find out how to get a more even firing I would aim for a blue flame at
the middle spy with as little orange as possible.

I found it helpful to have a piece of brick in front of each burner to
help gas and air mixing.

I always tried for just a bit of flame at the bottom spy.

A good way to evaluate overall reduction - if you can see around your
main damper - flame there will tell you a lot.

RR

[Robert D. Hill via Clayart]

Thanks Ron.

A lot of great real world advice in your post.
I will definitely be adding a target brick in the next firing to push more
heat up and to break up the flame for a better air/gas mixture. Would you
suggest a small brick near the burner port to break up the flame as well as
a larger target brick further along the flameway?
Thanks also to Mel for directing me to the achives, a treasure trove of info
there for sure.

Any other advice will be appreciated.
Dan Hill
Hill Pottery

-----Original Message-----
From: ron...@ca.inter.net <ron...@ca.inter.net>
Sent: November 15, 2025 1:30 PM
To: Clayart international pottery discussion forum

[ronroy--- via Clayart]

Hi Dan,
Great memories of our stay with you.

I used a 2 inch square high temp hard brick with the sharp towards
the flame - you may need a taller one - just to add some turbulence to
help the mix.

I'm not sure which shape of brick to use to force the flame up - you
might try different ones on each side to see what works best - how far
in front of the burner is decided by where the colder spots are at
the top.

I don't know if it's an option for you but - my flue ran the whole
length of the floor from back to front. That way I could arrange the
bricks over the flue to draw more or less flame from front to back.
You might be able to do that with shelves.

Just keep the basic rule in mind - direct flame to where you need heat
and reduction.

Maybe I should just come up there and show you what I mean?

RR

RR

[d jungle via Clayart]

Dan, why only 11" WC pressure with propane? I use a high pressure
regulator and use .5-3 lbs gas pressure and can control the reduction and
get a firing in under 5 hrs in the small flattop kiln out of Nils and Mel's
books. I also aim the torches to diff areas... Top corner and bottom
corner to get better heat distribution. Hope you use the double venturi
stack. It creates great draw and turbulence.
Good luck
Don

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[Robert D. Hill via Clayart]

Hi Don

11" WC is the pressure that is allowed by my propane supply company. Although the installer showed me how to boost the pressure to 15". There is an adjustment screw inside the cap of the regulator. The burners have a maximum btu rating regardless of the gas pressure feeding them. That is determined by the orifice size.

Can you explain how you aim the torches,(burners), to different areas?
I have 2 burners coming in from the back on either side of the chimney. For the next firing I will be adding target bricks to move the heat up and towards the back of the kiln.
I will also try Rons' idea of a small piece of brick just inside the kiln and in front of the burners to break up the flame, hopefully creating more turbulence and better gas/air mixing.

Yes, I have the double venturi stack and plenty of draw.
Dan
Hill Pottery