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I'm beginning a kiln conversion/update project and thought I would create a thread here for those interested, and to get feedback as I go along. I have access to a late 1950's Alpine kiln, and now have a place to fire it. It's been sitting for a long time, but I believe will be perfect with a little time and TLC. All the bones are solid, and other than some rust on the exterior, I think it will work great (estimated 12-14 cubic feet). My primary interest is having it as a cone 10 reduction kiln, specifically to experiment with shinos.  The kiln was originally designed as an updraft kiln, two forced air burners entering low on either side of the front next to the door. As I've read these kilns could be hard to fire evenly, I'm converting it into a downdraft kiln with floor fire burner placement. Ill plug up the original vents on top and need to build an exit flue and chimney behind the kiln.  I've attached my designs for what I propose.  At this point trying to decide between MR-750 and MR-100 Venturi burners (4 total firing on Natural Gas). Would love to hear from you if you have any positive suggestions. Thanks and I'll keep you posted as it unfolds. 

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Edited by bwsaunders

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Use at least the MR 100s-I have used both of those in many kilns-Hopefully you are using more than two-the more burners the more even firing. I would use 4 burners.

 

Edited by Mark C.

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35 minutes ago, neilestrick said:

They're not difficult to fire evenly. You just can't rush them. With a little practice they'll fire every bit as evenly as any other kiln. I would give it a shot before going to all that work.

Hi Neil.  As none of the original burner/blower system remains, and as it's going to be cost prohibitive to rebuild it, I will need to modify the burners as outlined either way. As for the chimney, I need to cut a hole in the roof out of the firing area and add a storm collar, etc. and wont be able to move the chimney once it's installed (and there is only one position for the kiln, so I can't shift it). If I fire it updraft with the new burners and don't like it, I'll be stuck. For that reason,  I'm going to stick with this updated design. Building a chimney out of softbrick isn't that complicated or expensive, even with the costs of welding the frame out of angle iron.  Thank you for the suggestion though. If I had the option to build everything out and test fire it as updraft,  without being locked in, I would. 

Edited by bwsaunders

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10 minutes ago, bwsaunders said:

Hi Neil.  As none of the original burner/blower system remains, and as it's going to be cost prohibitive to rebuild it, I will need to modify the burners as outlined either way. As for the chimney, I need to cut a hole in the roof out of the firing area and add a storm collar, etc. and wont be able to move the chimney once it's installed (and there is only one position for the kiln, so I can't shift it). If I fire it updraft with the new burners and don't like it, I'll be stuck. For that reason,  I'm going to stick with this updated design. Building a chimney out of softbrick isn't that complicated or expensive, even with the costs of welding the frame out of angle iron.  Thank you for the suggestion though. If I had the option to build everything out and test fire it as updraft,  without being locked in, I would. 

Understood. I didn't realize you were going to have to modify it anyway. Sounds like a fun project.

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This may sound strange but that kiln looks like its in Arcata from your photo-if thats a yes I know that kiln-it was last used as a sculpture lab burn out kiln at HSU.

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4 hours ago, bwsaunders said:

Hi Mark. Yes, it's in Arcata.  It was donated to FireArts, but has been sitting a while. Looking forward to getting it going again. 

I would recognize Peter Brants backyard anywhere.We are old best friends

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Wanted to post an update. Since I first posted, the kiln has been repainted (in progress in the photo), moved just outside the studio area and a kiln footing poured. As the 4 burners will be firing up into the side fireboxes, more height was needed than that from the 6" legs (removing the old rusted wheels so the feet set solid on the pad. I'm waiting for the cement to dry and will hopefully have our neighbor use their forklift next wed and move the kiln into position, and then I can add the structural bolts to secure it in place. With help, I've rerouted the gas lines and added a shutoff, and now need to build the burner/pilot manifold and hook it up, and build the chimney. I'll be building the manifold with 4 MR-750 burners, and the chimney out of soft brick (tied in with some angle iron and iron webbing.  I secured a nice stack out of stainless steel, and feel pretty good about my design for the chimney. The only thing I'm still looking into is shelves. Towards the bottom, a 32x20" shelf area would be optimal, with that tapering towards 24x20" towards the top. I was thinking of buying (4) 20x20" shelves and cutting each of them down to 16x20's. I hate doing that, but I don't know of any that size, and I'd like to use as much space as possible. Any ideas?  

Mark, picked up the colloidal silica and the milled zircon for the kiln coating from Phoenix today. Will probably spray the bricks once I get the kiln in place and finish up doing the cutting for the new exit flue. 

More as it happens. Hoping to have it firing by May 1. :)

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Why do you need to shelf stack to taper? I would use the same size shelves as the original. You'll want to leave room in there for a bag wall, and give the kiln room to breathe. Don't try to fill it too tight or you'll run into problems.

You may want to consider filling in all the gaps in the old bricks with some sort of castable material.

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Neil, well, as I have it designed, there would be a 5" channel following the taper off the interior walls from the fire box all the way up. I'm not sure about what size shelves were originally used, but would love to know if you do. If I do use a row of bricks on each side of the firebox, I'd have 27" of space along the bottom ( side to side)  which I may do to avoid having the bottom row get too hot during during. What size would you suggest?

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It probably either used two 11x28 or two 14x28. You may have a hard time finding 11x28 shelves, though. The original kiln used kiln shelves for a bag wall, but that was a crappy design because they'd warp really badly. I'd use bricks. You could always cut them down a bit to make a little more space. The bag wall will not only keep the flame off the bottom shelf, but in a downdraft kiln it forces the flame to go upward before being pulled down and out the flue at the bottom. Bag wall adjustments will make a huge difference in helping the kiln to fire evenly top to bottom. If the top tends to fire cold, raise the bag wall. As little as 1/2 a brick in height can make a big difference. You can also leave gaps between the bricks, etc. it's a great way to dial in evenness.

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Wanted to post an update as its been a couple months.  Since I posted last the kiln has been moved onto the foundation and bolted down, had a frame welded for the chimney and the stack cut in through the roof,  and most of the burner manifold built. Once we get the union aligned, it will be time to build the chimney and move closer to first firing. So nice to see a project coming together after a long time. 

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bw-

You might also consider mounting a poece of metal flashing about an inch + from the gas line. You could put a bend in it so that it shields the gas line from both the burner and the kiln floor.

Regards,

Fred

Edited by Fred Sweet

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three comments: 
1.   The updraft gas kilns at the local college have similar burner and piping arrangements as being used here and have shown no evidence of being overheated in the 12+ years I have observed them.   The piping has only the galvanized and paint coatings from the manufacturer.   The kilns are fired 1 to 2 times per week during the three semesters each year. 

2.   If you wrap the piping, be sure you thoroughly inspect the piping and structural members for corrosion prior to each firing.   Piping in an environment with high humidity and an insulating covering will be subject to hidden pitting corrosion underneath the insulating material; the risk is especially increased when the piping is only heated periodically.  

3.   Consider the effects of wind blowing across the kiln area floor and interfering with the burners and pilots.   You might need to add some portable windbreakers.  Even though the college kilns are in a large shed with half walls on three sides (full wall on one),  high wind conditions have shut down the kilns by blowing out the burners/pilots.   Portable wind breaks are used to mitigate the winds. 
  

LT
 

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Instead of wrapping I favor the sheet metal shield. The pipe will not corrode that way and its all out in the open for inspection.

The other suggestion is painting the pipes with high heat silver paint-comes in a spray can is aluminum colored and really reflects heat well. It holds up super well to high heat situtaions.I spray all my gas lines close to kilns with it. Hensells hardware sells it in paint Dept.

I also spray all my kiln metal work with it before the rust sets in.It protects for decades.

Edited by Mark C.

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