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Building A Shed For 7' Tall Gas Kiln


Roberta

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I just joined today so please go easy on me . . .

 

I'm a fairly experienced student and I love cone 10 reduction. My only kiln firing education experience was very limited and over five years ago, at a well-equipped big city community college with huge kilns burning natural gas. I was a newbie just following precise instructions from the instructor, so I'm just about completely ignorant in practice.

 

I am now 500 miles away on a small farm with the new-to-me 12 cubic ft updraft kiln all hooked up to my 250 gal propane tank. The kiln is 7 ft in height including the ~ 2' iron stand. There is also a pyramidal sheet metal hood on top, which adds another foot for a total of 8' in height. Between droughts we get RAIN here in the winter and often it's falling "horizontally" and in summer quite a strong breeze in the late afternoon. In short, my kiln needs to be in an enclosure to keep it dry and the wind away from the burners. I want to build a permanent shed around it. I have a few questions related to that:

  • How high above the kiln vents should the metal ceiling of the shed be?
  • What's the ideal size for an opening in the shed ceiling above the vent for a kiln this size being fired to cone 10?
  • This opening will be covered with a rain cap so I can fire in winter, too. Will heat pretty much go straight up and out of the vent? I'm thinking the rain cap is going to get extremely hot, is that correct? How far above the kiln vents should it be? i.e. does it need to be on top of a wire "stovepipe" or something like that?
  • Any suggestions for "room size" for the shed? I know I'll be needing to control air to fuel ratio using the vents at the top and will need some space for moving around to do that safely.

Fortunately on ag zoned land few regulations seem to apply to what we do out here and we are avid about keeping brush cleared, etc. for fire safety. Also I've met a retired ceramics teacher and she is going to fire her own pieces and help out/oversee/advise once I start to actually use the kiln. Plus one of the propane company guys is interested enought to want to see it in action, so once we're firing things should be safe and sane, despite my being totally in over my head.

 

All my best,

Roberta

 

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I am more familiar with downdrafts, but I had an Olsen draft at my last college teaching job. The setup had a hood over the whole kiln and then a stack the exited through the roof about 10 ft. above.  The kiln was about 100 cu. ft.  I think it would be a good idea for a hood to capture the heat and go through the roof.

 

Marcia

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Thank you so much for responding, Marcia. That sounds quite a lot like the set-up of the large kilns I fired on at Glendale Community - the kiln had a hood, was in a big warehouse like facility, etc.

 

My kiln up here already has a hood, so if I have my shed roof shaped like a hood, it's sort of redundant, right? The other alternative is a removeable roof, that just covers it the kiln, and no firing during wet winter weather, which is sporadic anyway most years in Northern Calif. Maybe that's the simplest way to deal with the unknown of how much heat is being generated and what the height and distances will need to be. I'll wait to see if anyone else has some info on this.

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I would make it a metal roof at least 3 feet above kiln top. Since you have a hood you can run a metal stack thru the roof (plan on wood members being away from the penetration )

Make the shed plenty large in all dimensions so the wood is far away from kiln. Make room for some storage of kiln furniture and a place to dry pots in warm shed. Larger kiln sheds always work best -small ones are a pain.

Mark

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roberta, if you are in northern california, and Mark is in northern california, why not set up a visit to his studio in the Arcata area?  (then you can tell us all about our favorite gas firing potter.)

 

Mark, when you DO retire, not for a long time, why not leave everything in place and offer tours to traveling potters?  bet there would be lots of us.

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Thank you so much for responding, Marcia. That sounds quite a lot like the set-up of the large kilns I fired on at Glendale Community - the kiln had a hood, was in a big warehouse like facility, etc.

 

My kiln up here already has a hood, so if I have my shed roof shaped like a hood, it's sort of redundant, right? The other alternative is a removeable roof, that just covers it the kiln, and no firing during wet winter weather, which is sporadic anyway most years in Northern Calif. Maybe that's the simplest way to deal with the unknown of how much heat is being generated and what the height and distances will need to be. I'll wait to see if anyone else has some info on this.

Maybe you only need walls on the windward side(s)? Or walls that go up 5-6' and leave airspace/breathing room/light, with a deeper overhanging roof. With an updraft, you'll probably still need to vent out the roof, but I think a rain cap isn't really necessary - little rain is likely to enter (check with Mark C. on this since he knows your area) when not firing and when you are, rain will evaporate before it hits! I have stood in the rain beside my mortarless brick catenary while it was firing and been completely dry kiln-side! We used to cover it with a giant Baggie between firings in wet weather before the roof went up.

I envy your 2' stand, my Geil is so close to the ground that it requires some contortions to clear burner lines of spiders, who seem unfazed by gas!

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I would make it a metal roof at least 3 feet above kiln top. Since you have a hood you can run a metal stack thru the roof (plan on wood members being away from the penetration )

Make the shed plenty large in all dimensions so the wood is far away from kiln. Make room for some storage of kiln furniture and a place to dry pots in warm shed. Larger kiln sheds always work best -small ones are a pain.

Mark

Hi Mark,

I'm in Lake County, 200 miles south and east of you. Thanks for the advice on a roomier shed. It makes a lot of sense. Could you please just clarify regarding the metal stack - should I have a welder add that right onto the existing hood? I've been advised to use a kiln shelf set on the opening of the hood so it can slide back and forth to control the atmosphere during reduction. Does that make sense? I would need to figure out how I could still do that if a stack is added to the hood.

~ Roberta

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Roberta

I took some photos today of my flue hood and roof jack to give you some ideas -I will add them later tonight after work.Today is alot of chores along with a large kiln to unload.

On your updraft you need a part of a shelve that slides over the opening in roof to control reduction.This need to close off the flue completly as well when fire is done.

This shelve usually has a control rod that is bolted to shelve to make it slide-is your kiln missing this item? Mine is on roof of kiln. The hood fits over the kiln usually a few feet above the kiln and collects heat to a round or square smaller opening-this vents thru a roof jack. Since this all get very hot its supported by metal not wood.

I got all my stuff at a salvage yard over time-my galvanized hood rusted out a few years ago and I found a stailess one for $25

My vent roof jack is also a spun aluminum restaurant large roof jack from yard aslo $25s.

Mine is a bit overkill but thats my style as it gets used alot.

Regular sheet metal will last years-you can have one made or scrounge one up.

Lake county is a big place where are you as there are many potters spread around there.?Cobb mountain seems to have afew as well.

Posting a few photos of kiln top would help as we are giving advice on large unknown objects.

Photos are easy to post-just read the how to here

http://community.ceramicartsdaily.org/topic/5843-our-most-frequently-asked-questions/

Mark

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roberta, if you are in northern california, and Mark is in northern california, why not set up a visit to his studio in the Arcata area?  (then you can tell us all about our favorite gas firing potter.)

 

Mark, when you DO retire, not for a long time, why not leave everything in place and offer tours to traveling potters?  bet there would be lots of us.

Oldlady,

I have way to much stuff ever to think about getting rid of it. I never plan on undoing my ceramic part and it will always be in place.Kilns will stay and my wife will deal with it. Our estate is going to my nephews unless my wife sells the place to another potter if she needs the $. The trouble with that is you see this all the time in the ads of CM as the boomers retire and try to sell to other potters which these days are less and less.

Hey if anyone is in my area (as its only on the way to Redwood national park) I'm sure a quick tour would be no problem.Just give me aheads up.

Mark

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Roberta

I took some photos today of my flue hood and roof jack to give you some ideas -I will add them later tonight after work.Today is alot of chores along with a large kiln to unload.

On your updraft you need a part of a shelve that slides over the opening in roof to control reduction.This need to close off the flue completly as well when fire is done.

This shelve usually has a control rod that is bolted to shelve to make it slide-is your kiln missing this item? Mine is on roof of kiln. The hood fits over the kiln usually a few feet above the kiln and collects heat to a round or square smaller opening-this vents thru a roof jack. Since this all get very hot its supported by metal not wood.

I got all my stuff at a salvage yard over time-my galvanized hood rusted out a few years ago and I found a stailess one for $25

My vent roof jack is also a spun aluminum restaurant large roof jack from yard aslo $25s.

Mine is a bit overkill but thats my style as it gets used alot.

Regular sheet metal will last years-you can have one made or scrounge one up.

Lake county is a big place where are you as there are many potters spread around there.?Cobb mountain seems to have afew as well.

Posting a few photos of kiln top would help as we are giving advice on large unknown objects.

Photos are easy to post-just read the how to here

http://community.ceramicartsdaily.org/topic/5843-our-most-frequently-asked-questions/

Mark

Thanks - when temp drops below 100 here, will go out and take some photos of what I've got so you can see. ~ Roberta

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Here are those photos

The hood on roof which has custom flashing so rain will not leak down-its a small flanged box that you will see under hood on green roof

The stainless hood is hanging by chain over 12 cubic updraft-you can see the space-its cluttered with old pots from raku to salt -all are dead/dunted/cracked-I like em still as art-some are made by others

The close up shows fiber tubes cut to insulate from heat-its worked well for 35 years

The stainless hood is newer as the galvanized one rusted away

the worded sign is behind kiln and is metal heat shield  and keeps the heat away from other item behind kiln

My space is well used

Mark

post-8914-0-24285600-1435543669_thumb.jpg

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post-8914-0-15917400-1435543692_thumb.jpg

post-8914-0-33703200-1435543705_thumb.jpg

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Here are those photos

The hood on roof which has custom flashing so rain will not leak down-its a small flanged box that you will see under hood on green roof

The stainless hood is hanging by chain over 12 cubic updraft-you can see the space-its cluttered with old pots from raku to salt -all are dead/dunted/cracked-I like em still as art-some are made by others

The close up shows fiber tubes cut to insulate from heat-its worked well for 35 years

The stainless hood is newer as the galvanized one rusted away

the worded sign is behind kiln and is metal heat shield  and keeps the heat away from other item behind kiln

My space is well used

Mark

Much appreciated! Here are my photos.post-68957-0-32491300-1435550290_thumb.jpgpost-68957-0-77623500-1435550302_thumb.jpg

post-68957-0-43963900-1435550325_thumb.jpg

post-68957-0-32491300-1435550290_thumb.jpg

post-68957-0-77623500-1435550302_thumb.jpg

post-68957-0-43963900-1435550325_thumb.jpg

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I would raise the hood up so you can access the kiln roof.The damper need to be on kiln roof.Also the flue exit looks like maybe a brick is missing or broken off as that flue looks large unless the kiln is large.

How many cubic feet is it?

also is it hard brick with a fiber liner?The arch looks like soft brick.

Is the fiber glues in?

I have nevers een an updraft with the hood on top and not raised. Are you sure there is no damper on roof under that hood?

Mark

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roberta, the kiln is "new to you".  was it in place when you bought the place or was the kiln shipped to you?  i would bet that someone simply put the hood on top of the kiln to make the whole thing easier to handle in transit.  that is why it doesn't make sense to mark, the hood was never intended to be used there but suspended above the kiln once  it was set up.

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I would raise the hood up so you can access the kiln roof.The damper need to be on kiln roof.Also the flue exit looks like maybe a brick is missing or broken off as that flue looks large unless the kiln is large.

How many cubic feet is it?

also is it hard brick with a fiber liner?The arch looks like soft brick.

Is the fiber glues in?

I have nevers een an updraft with the hood on top and not raised. Are you sure there is no damper on roof under that hood?

Mark

Answers to your questions:

It's clear to me now that the hood needs to suspended and it is just sitting on top so it's out of the way and not on the ground - we had the whole thing tarped until the last storm passed some weeks ago.

The interior is 12 cubic feet

I guess I better find out from Gregg Lindsley who rebuilt it how the fiber is attached. Also he only really fires electric, so I knew I'd be pretty much on my own figuring things out, and he highly recommended this site, so here I am.

The top isn't regular brick, it's the thermal type. Gregg wouldn't have used soft brick!

There is no damper - there never was one made for this kiln and he told me when he brought it over that I'd need to make one and I think I sort of looked dumb and said uh, okay, when he told me to use a kiln shelf. Very mystified because this isn't really discussed in any book I've seen including Nils Lou's! Barbara finally filled me in that it's a shelf with a metal rod attached to it so you can move it and she said that during firing some very minute adjustments will be needed. I'm trying to figure out how such a haphazard seeming rig is used to precisely control the atmosphere for reduction firing as it doesn't have any real framwork for keeping it in the correct position.

This is the first I've heard that the flue is large, too, so I hope the damper can compensate for that.

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You will need some angle iron guides welded to the frame to hold the kiln shelf in place when you slide it. Be sure they are spaced well away from the vent so that the sliding doesn't dislodge stuff into the kiln. Make little walls of soft refractory brick that you can cut to fit any space between the angle iron and the kiln top (castable or fiber would work, too, but are more fragile). Use two shelves that meet in the middle and only slide one of them. I think at the beginning you will like to have some sturdy steps up on the side of your kiln so you can see what's going on. Later you can mark the damper shelves at the edges with grinder notches for your desired settings.

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I know Gregg Lindsley say hi from me. He put togther a potters guild workshop in Mendocino a decade or two ago I attended.

He gave me a potters music cd at a party a few years back as well near my house.If I recall he is in cobb mountainarea.

small world you know .

 

PS soft brick are super insulating and they are what you want for a reduction kiln like yours.

Hard brick use more energy to heat up and they are great in salt and wood fire kilns that are rough on inner chambers

Mark

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You will need some angle iron guides welded to the frame to hold the kiln shelf in place when you slide it. Be sure they are spaced well away from the vent so that the sliding doesn't dislodge stuff into the kiln. Make little walls of soft refractory brick that you can cut to fit any space between the angle iron and the kiln top (castable or fiber would work, too, but are more fragile). Use two shelves that meet in the middle and only slide one of them. I think at the beginning you will like to have some sturdy steps up on the side of your kiln so you can see what's going on. Later you can mark the damper shelves at the edges with grinder notches for your desired settings.

Hi Rae,

Thanks for this - I'm getting a bit better picture now. The vent has 2 openings, so will the two shelves each cover half or does one cover the front and one the back? Or does it not matter?

What is the purpose of the pieces of brick to fill the gap beneath the angle iron? to keep air out of the vent?

Best,

Roberta

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I know Gregg Lindsley say hi from me. He put togther a potters guild workshop in Mendocino a decade or two ago I attended.

He gave me a potters music cd at a party a few years back as well near my house.If I recall he is in cobb mountainarea.

small world you know .

 

PS soft brick are super insulating and they are what you want for a reduction kiln like yours.

Hard brick use more energy to heat up and they are great in salt and wood fire kilns that are rough on inner chambers

Mark

I will say hi to Gregg for you and oops I did get the types of brick reversed - I was reading about that a couple weeks ago, too. Is your damper similar to what Rae described?

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Roberta

This is what my small kiln updraft roof with flue looks like-you can see the steel rod that slides the piece of kiln shelve to make an air tight seal when closed-this is also the way to control reduction.

Mark

 

post-8914-0-59870500-1435782471_thumb.jpg

post-8914-0-59870500-1435782471_thumb.jpg

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You will need some angle iron guides welded to the frame to hold the kiln shelf in place when you slide it. Be sure they are spaced well away from the vent so that the sliding doesn't dislodge stuff into the kiln. Make little walls of soft refractory brick that you can cut to fit any space between the angle iron and the kiln top (castable or fiber would work, too, but are more fragile). Use two shelves that meet in the middle and only slide one of them. I think at the beginning you will like to have some sturdy steps up on the side of your kiln so you can see what's going on. Later you can mark the damper shelves at the edges with grinder notches for your desired settings.

 

Hi Rae,

Thanks for this - I'm getting a bit better picture now. The vent has 2 openings, so will the two shelves each cover half or does one cover the front and one the back? Or does it not matter?

What is the purpose of the pieces of brick to fill the gap beneath the angle iron? to keep air out of the vent?

Best,

Roberta

Hi, Roberta,

The gap needs to be filled because you want to have the maximum control over the amount of atmosphere you release, or contain. You don't want extra flames squirting out around the opening, if possible. It's preferable to operate it from the side of the kiln.

Mark C's solution is much more elegant than the one I used - get it if you can!

Good luck,

Rae

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Just ask Greg about the damber setup on that kiln-he should address this easy as he made it.

Mark

LOL, just got off the phone with him. He says Hello! to you and I learned that I misunderstood the extent of work he did on the kiln - it was basically insulating the interior, not completely rebuilding it. He got it from another potter, made the upgrades and never touched the flue. He'd never fired it so had not made a damper. He was really helpful and we found a source for a refractory cement that is good to 2600 F and I'll be able to fix the top of the flue which not level at all so that I can rig a damper up that will sit on it properly. Anyway, I think I'm on my way now and thanks for the advice. The photos were really helpful.

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You will need some angle iron guides welded to the frame to hold the kiln shelf in place when you slide it. Be sure they are spaced well away from the vent so that the sliding doesn't dislodge stuff into the kiln. Make little walls of soft refractory brick that you can cut to fit any space between the angle iron and the kiln top (castable or fiber would work, too, but are more fragile). Use two shelves that meet in the middle and only slide one of them. I think at the beginning you will like to have some sturdy steps up on the side of your kiln so you can see what's going on. Later you can mark the damper shelves at the edges with grinder notches for your desired settings.

Hi Rae,

Thanks for this - I'm getting a bit better picture now. The vent has 2 openings, so will the two shelves each cover half or does one cover the front and one the back? Or does it not matter?

What is the purpose of the pieces of brick to fill the gap beneath the angle iron? to keep air out of the vent?

Best,

Roberta

Hi, Roberta,

The gap needs to be filled because you want to have the maximum control over the amount of atmosphere you release, or contain. You don't want extra flames squirting out around the opening, if possible. It's preferable to operate it from the side of the kiln.

Mark C's solution is much more elegant than the one I used - get it if you can!

Good luck,

Rae

 

Thank you Rae and see my response to Mark. The top of the flue is far from level, rather a mess actually but we have a solution and I'll be letting you and Mark know how it worked soon I hope. ~ Roberta

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