What is the smallest gas-fired kiln I could build to fire a 24"x18"x5" pot to cone 10?

[BillsBayou]

I'd like to begin the journey from know-nothing to creating my own extra-large pots. Before I begin, I want to know what the destination exists.

I've seen home-made kilns on YouTube and such so I have it in my head that it's possible to do this in my backyard. I need help figuring out what it would take to build a gas-fired kiln capable of making pots for the large bald cypress trees I collect. Since it's my suburban backyard, the only limit to my project is the footprint I can dedicate to the kiln. Hence the question I have in the thread title.

 

[garywood]

Bill, to begin with, it's just not cost effective to fire one pot at a time. If that's not an issue, you'll need about 3" or so space for heat circulation to prevent hot spots. Depending on your burners maybe a little more. I've built several and I've found it's best to have plenty of room. Will your burner(s) be bottom or side(s)?

 

[BillsBayou]

Bill, to begin with, it's just not cost effective to fire one pot at a time. If that's not an issue, you'll need about 3" or so space for heat circulation to prevent hot spots. Depending on your burners maybe a little more. I've built several and I've found it's best to have plenty of room. Will your burner(s) be bottom or side(s)?

Using 3" as a base rule, I can begin to understand the footprint requirements. I'm literally building my concept from the ground up.

When you say it isn't cost effective, what do you mean? If I were to guess, I'm assuming that the energy required to fire one pot is roughly the same amount of energy required to fire a much larger volume of pots. If I'm going to use up that much gas and time, I could have ended up with a dozen pots instead of just one. Something like that?

Since your initial response was "You're nuts. You can't do that." it feels like I'm not nuts or on the wrong track. I want to minimize the footprint of the kiln, so with a 24-inch pot, plus 3" clearance and a little more for breathing room, I build a kiln with an interior floor space of at least 32"x 28". I wouldn't know if bottom or side burners are better.

I don't even know what type of gas I'm using. What's the recommended type and just how much gas am I'm going to be burning up?

 

[garywood]

Bill, I didn't say you are nuts ;-) unique ;-) I use natural gas but propane is used as much, orifice size is different. Will you be using natural draft or forced air? I've used both but prefer forced air. Forced air is usually side burner with at least 4" flame way and natural draft is usually bottom. Google kiln burners when you finalize your size to get the right size burner and flue opening. Have fun!

 

[garywood]

Bill, decide what size kiln shelves you will use and start there. They come in a large variety of sizes so figure the shelf(s) and add your clearance from there.

 

[BillsBayou]

Bill, decide what size kiln shelves you will use and start there. They come in a large variety of sizes so figure the shelf(s) and add your clearance from there.

I figured I'd want to look into kiln furniture before finalizing the size of the footprint.

I'll probably go the forced-air approach, by the way.

The real issue with all of this is that I don't know what I don't know. Finding the right "first questions" to move me forward is very awkward. Kiln furniture and burners will be the initial searches. Then I'll move on to bricks and construction methods.

If my wife finds out I'm attempting to add pottery to my skill set, she's going to scream so loud, my ears will bleed.

 

[Anthony]

You can render clay vitreous from as low as 720 deg,C.
Talk to Sorce, he has a book with clay body formulas.
Our pots are vitreaous at 980 deg,C

With a lower firing, the cost becomes minimal.

Mr.Valavanis had two books on Conifers and Decidiuous trees.
There were two articles on making pots,
One showed the guy with a single pot firing kiln.
Talk to him, see if he still has copies.

At cone 08 you can go electric and save $$$
or try solar firing [ since the 70's ]

Use technology to save $$
Good Day
Anthony

 

[WNC Bonsai]

I made my wife a Raku kiln once. Basically consisted of a fire brick base and a galvanized trash can lined with batts of a high temp silica ceramic fabric that looks like white insulation. I used a propane gas burner from wardburner.com. She used it a while then sold it when she stopped doing raku. Worked well as long as you allowed it to warm up slowly then cranked up the gas to full flame. Do it too fast and you can hear the pots cracking due to rapod expansion. One thing to be aware of is some communities have strict zoning requirements for kilns becasue the heavy metals used in many glazes end up being exhausted during firing. You might want to try your hand at cement pots—no kiln needed and much lower tech. I just bought a bag of portland patching cement and a sheet of metal stuco lathe yesterday for that purpose.

 

[Sekibonsai]

I would suggest taking a basic pottery course first. Its not as simple as a youtube video would have you think- slap some clay slabs together... and some firebrick and go. The difficulty goes up immensely as the size of the pot increases. That is why pots are more expensive as the size increases- think about 1:! or 2:1 losses....

And as Cofga alludes to I would consult with your local fire marshal and permitting agency. Ask about a backyard pizza oven and see what they say.

 

[penumbra]

I would suggest taking a basic pottery course first. Its not as simple as a youtube video would have you think- slap some clay slabs together... and some firebrick and go. The difficulty goes up immensely as the size of the pot increases. That is why pots are more expensive as the size increases- think about 1:! or 2:1 losses....

Ditto, from a potter. Slab work on large pots in particular is much more difficult than it looks. Consider;
Time to make a decorate pot, hours, usually stretched out over a couple days.
Drying time, about a week, could be more.
Bisque firing, 12 to 14 hours, or more.
Glaze, an hour or so.
Final firing, 14 hours gas or electric, wood about 2 days.
And keep in mind that you are married to the project during each of this steps. During the slab building process your life revolves around the clay as it goes through different drying and setting processes that enable the assembly. There are tricks you will learn along the way but generally you can't start a pieces and then decide you want to take some time off. You need to be there. Potters can have a pretty lonely life, except for other potters, more than half of whom will not agree with your procedure.
Clay is great if you love the process and can devote yourself to it.

 

[Lionheart]

I would suggest taking a basic pottery course first. Its not as simple as a youtube video would have you think- slap some clay slabs together... and some firebrick and go. The difficulty goes up immensely as the size of the pot increases. That is why pots are more expensive as the size increases- think about 1:! or 2:1 losses....

And as Cofga alludes to I would consult with your local fire marshal and permitting agency. Ask about a backyard pizza oven and see what they say.

They don't deal well with the term: kiln.

 

[penumbra]

Something I forgot to address. It does take quite a bit more fuel to fire one pot than several. You want that kiln to be as full as possible.

 

[Hyn Patty]

Being a ceramist myself, I agree with what the others are saying. Learning ceramics is a lot like learning how to do bonsai. It takes time and study, not just building the kiln. NOT that I wish to derail you. It's a great thing to learn how to do but it is a bit more complicated than you might think. It could take you a few months or even a few years to get the hang of making large pots. You'll lose plenty of them to cracking, pitted glazes, all manner of screwups until you get the hang of it. Taking a few classes to learn how to hand build or throw smaller pots would be highly advisable as a first step before you begin investing in building a kiln. Learn the basics first, and learn about how a kiln works and how to load it, and let someone else fire them for you until you are ready - else you may invest a few grand in materials and then realize you have no idea why things don't work right.

 

[sorce]

@BillsBayou. Nice! You sure won't get better NOT Doing!

I spoke with my most local city woodfirer...
Wood is more acceptable in city limits because if left alone, the fire will go out.
Gas, if left alone, can keep climbing in heat and kill people!

I'm working on a woodfire design using electric kiln bodies, as Firebox, and chamber.

I've seen MAD free\cheap used kilns down south. Get some!

This local woodfire is a fast fire design.
Fast being 8-24 hours.

If the interior is lined with soft brick less time is needed.
Hard brick means more time to reach temps.
Outer insulation also makes a difference.

Start with an understanding of this materials difference, and begin with a known design.
Otherwise you may never figure out you need a partner to fire your kiln for over 24 hours....or...you can start a meth habit and do it yourself! Joke. Bad joke? Oh well!

You can scale this design up or down.

Someone mentioned expansion and contraction.

Ive read about steel cables used as chimney Tie downs that broke and near killed people from exp and con.

But chimney is important for draft.

Forced air or piss money away though for sure.

The Aussies have the best DIY IMO.

Love me some kilntalk.

Kill. South south.

Sorce

 

[SU2]

I made my wife a Raku kiln once. Basically consisted of a fire brick base and a galvanized trash can lined with batts of a high temp silica ceramic fabric that looks like white insulation. I used a propane gas burner from wardburner.com. She used it a while then sold it when she stopped doing raku. Worked well as long as you allowed it to warm up slowly then cranked up the gas to full flame. Do it too fast and you can hear the pots cracking due to rapod expansion. One thing to be aware of is some communities have strict zoning requirements for kilns becasue the heavy metals used in many glazes end up being exhausted during firing. You might want to try your hand at cement pots—no kiln needed and much lower tech. I just bought a bag of portland patching cement and a sheet of metal stuco lathe yesterday for that purpose.

What a great wealth of info in 1 post

Will say my feeling's the same, it's portland alllll the way for me it's not even just practicality I genuinely prefer the aesthetics (and am surprised this isn't the norm, actually....even 'ok' finished 'crete looks SO much more 'natural' than ceramics, am sure I'm in a small minority% but I think glazed pots look silly/cheesy and completely undermine the natural beauty of the tree holding them in almost-every instance I've ever seen) But w/ portland-based pottery you can fix/patch, you can 'work-up'/build-up projects real easily, the only real drawback I've found or could even think of is that you need to leach them a bit before usage, but that's just planning/patience which is par-for-course in this hobby anyways!

IF I were going for clay -- which I almost did myself actually -- I'd definitely setup similar to how you mention, I'd setup a forge last year (aluminum, copper, zinc etc) that didn't even need / get hooked-up-to the propane kit i'd bought for it, simply having forced-air via a hair-dryer (and a tightly-sealed forge of course) was plenty to liquify metal so cannot imagine it being hard to adapt/scale it for ceramics (on youtube, King of Random had some of the simplest tutorials for backyard forges, typically with propane and the more-costly refractory bricks but simply lining the kiln/forge with cement or plaster-of-paris worked well for me (turned out making quality forms was wayyyyyy harder than expected so project was ultimately abandoned)

Gah for Bill's amazing BC's my mind would never go to ceramic it'd be masonry-only because, practicality&aesthetics aside, there is an inherent "burly" quality (even if just psychologically) to cement, and a 'fragile' one to ceramics....if I'm presenting a 5' tall, 3' wide-at-buttresses BC, unless it's some weird literati thing then I see it as an inherently 'masculine' aesthetic which'd be helped by crete / detracted-from by fragile ceramics!

 

[SU2]

Aren't there parts of the world where high-bonsai-culture has a norm of concrete-pots, not ceramics?

[also, to state the obvious, if you're not going for the rough/unfinsihed look of the 'crete pots then you're coating them anyways, if that's the case then I'm missing why it'd even matter whether it was crete or ceramic behind the painted/glazed exterior! Though IMO using stains on 'crete is the most-natural you can make slabs/pots]

Being a ceramist myself, I agree with what the others are saying. Learning ceramics is a lot like learning how to do bonsai. It takes time and study, not just building the kiln. NOT that I wish to derail you. It's a great thing to learn how to do but it is a bit more complicated than you might think. It could take you a few months or even a few years to get the hang of making large pots. You'll lose plenty of them to cracking, pitted glazes, all manner of screwups until you get the hang of it. Taking a few classes to learn how to hand build or throw smaller pots would be highly advisable as a first step before you begin investing in building a kiln. Learn the basics first, and learn about how a kiln works and how to load it, and let someone else fire them for you until you are ready - else you may invest a few grand in materials and then realize you have no idea why things don't work right.

Can't say I thought it'd be *that* much of a pain/learning-curve!! That^ just makes me even more confused at why cement pottery isn't far more popular, almost anybody can figure out how to make whatever it is that pleases them when mortar is the medium!