Noob Seeks Advice Building Kiln On The Cheap

[joff]

Hi, my name's Joff, I'm a Gringo living in rural Costa Rica.

 

I'm interested in building a versatile kiln on the cheap for small pottery projects and metal clay, and maybe other stuff.

 

I really have no idea what I'm doing- I've never taken a pottery class or anything, I've just read this and that on the internet.

 

I do have access to refractory bricks. My idea is that I would build the kiln each time based on the project size. I would add a heat source... and monitor the temperature... is this feasible?

 

I have few resources here. There is some pottery being done in the country, but no retail supply as far as I know. But even if there was, a retail kiln would be way out of my price range- the shipping and taxes are prohibitive.

 

I have access to propane and 220. I know a guy who works on appliances who could probably help me find a burner or heating elements. And like I said I know where to get good refractory bricks.

 

And I have people who come down regularly and are willing to mule stuff for me. In asking such favors size and weight is an important consideration.

 

I seek advice.

 

How should I heat it? What are the pros and cons? Cost is a factor both in initial investment and in use. Can electric elements be easily reconfigured to accommodate different kiln sizes? Is propane an ideal gas for a kiln? What exactly do these different heat sources require to function? What type of burner do I need for propane? What type of electric element is required for such heat? I'm thinking I can't just salvage it out of a broken toaster. Or can I?

 

How should I monitor the temperature? It needs to be cheap and small enough for a friend to bring down without pissing him/her off. I instinctually would rather have a pyrometer I can place inside- is there some reason I should prefer IR?

 

Can I do this for under $100? (Keeping in mind I'm looking for entry-level solutions and I may wish to upgrade when I understand their shortcomings through experience.)

 

What have I not taken into consideration?

Thanks.

[Benzine]

Welcome to the Forum.

 

This is a fabulous source of information, and kiln construction, is actually, what led me here years ago.  I was interested in building a Raku kiln, and I got some great advice, and ended up building a nice little kiln.

 

What you are talking about is a bit different.  My kiln is made to heat fast, and doesn't need to retain much heat, because of this.  

I am guessing that you want a kiln for bisque firing and for glaze firing?

 

I would first suggest that you do some research, into what exactly your goals all for ceramics.  What do you want to make, what kind of clay do you want to use/ what temperature do you want to fire to, etc?  This will all help others answer your questions.

 

Here's the down side to kiln building "On the cheap", as our current board Sensei John would say, "You get what you pay for".  If you buy cheap parts, you'll end up with said parts that don't work as well, and/ or last as long.  

 

A GOOD gas burner will cost over, what you want to spend on the whole kiln.  I bought a much cheaper version, because my tiny Raku kiln can run off of it.  I know it won't do as good as a job, but for how often I use it, and what it's used for, it works well.  

 

In terms of building a kiln, I will remain relatively silent, especially as it relates to the use of bricks.  I haven't built anything like that.

 

I will say, that many people just suggest finding an old electric kiln, and converting it to gas.  Here, in the US, old kilns, that people want to get rid of, are not that hard to find.  I'm not sure how things are there, but that is always a great option.  Who knows, you might be able to get an old kiln free, allowing you to just have to worry about a burner.

Also, yes propane works great for firing.  That's what I use for my Raku kiln.  Some people use Natural Gas as well.  Remember that when you look for a burner, you need to specify which fuel you'll be using.

 

In regards to electric kilns, the wires for kilns are VERY specific.  They have to be the right thickness, length etc.  Electricity can be a scary monster, if not properly respected.  Please do not try to take the wires from any other device, to use in a kiln.  

 

That's all I have at the moment.  I know others will add their insight as well.

 

Best of luck on your journey.

[joff]

Thanks for your response.

 

If I was in the 1st world I would absolutely get a second-hand kiln. But it's not like that down here.

 

And the other thing is- correct me if I'm wrong- the fundamentals are not terribly complicated. I need to apply, distribute, contain, and regulate heat. I realize that the specifics of how much and for how long get increasingly detailed like an earthenware mandelbrot set, but that the basic concept- heat it till it starts to melt- is pretty ubiquitous.

As I said I want something versatile. I have access to a wheel but no idea what kind of clay I will find. I live in a floodplain and I know there's clay 5' down. I'd like to give that a try. Maybe that's a fool's errand but that has something to do with why I don't want to spend a bunch of money... along with the fact that I don't have  much. There's a village a ways away that does pottery... I want to see what they use but I guarantee they dig it out of the ground and have no idea where it would be categorized on the pottery supply order form.

 

I know I also want to get some metal clay and mess around with that.

I'm leaning toward propane.

[Benzine]

The concept of firing clay is not that complicated, though you are not actually trying to "melt" the clay, just vitrify it.  However, the PRACTICE of firing a kiln, can be complicated, especially a gas or wood fire kiln.  A basic electric kiln, will have a couple knobs, that need to gradually be turned up.  This requires a little work, and keeping good record, to fire consistently.  I am fortunate enough, to have a computer controlled electric kiln in my classroom.  I set it to the desired program, and hit start.  The hardest thing I have to do, is check on it every once in a while, as it's firing.  

For comparison, here is a thread discussing a recent firing, in a gas kiln, that one of the forum members did:

 

http://community.ceramicartsdaily.org/topic/6039-real-time-kiln-advice-kiln-curently-firing/

 

To get consistent firings in any kiln, you have to know what you are doing, and continually document your steps for reference down the road.  It's not a matter of "Apply heat source, until the clay hardens."

 

The local clay that you mentioned might work, to some extent.  A lot of "Found" clay isn't great, because of all the other stuff in it.  I used some from a river, and while it looked nice, it was all types of brittle, even when fired. On top of that fact, think of all the labor you will have to do, in order to get the clay to a usable point.  There will be a lot of digging, drying, slaking, screening, drying, wedging, etc.  Clay, from a supplier is relatively cheap.  

There are a couple recent topics on the use of found clay, around these boards somewhere. 

[joff]

I have little doubt the clay down here is crap, as is the local pottery... it's supposedly traditional but is for mostly for tourists. It's more like a canvas to paint birds and frogs on.

 

http://wanderlustandlipstick.com/blogs/wandershopper/2013/03/26/glazing-traditional-potteryin-guatil-costa-rica/

 

I'm from the US- I know how weird it sounds that you can't buy clay or a kiln... but actually North America and Europe are rare exceptions in such varied retail endeavours. Just last year Costa Rica got it's first beer brewing supply retailer.

[High Bridge Pottery]

If you do have access to insulating fire bricks you could probably build a very simple electric kiln.

 

This video the guy is making a forge to melt aluminium but you can see how simple it is. Add a roof and you have a very small kiln with no temperature control and some interesting looking elements. The Kanthal wire he talks about is better for ceramic kilns. I have a small kiln that runs off 240 volts @ 13 amps that is much bigger than the one he has made. Not sure on the exact size but it can fit in 6 mugs easily.

 

Take some work figuring out the circuit, size and correct amount of insulation. Also a better design than his and some way of controlling the temperature.

 

 

[neilestrick]

If you can get firebricks and propane, and have access to pipe fittings, then you can build some very simple burners and a very simple kiln. Get Olson's 'The Kiln Book' for starters, as it will give you a lot of good information on what goes into building a kiln. But as Benzine mentioned, first you're going to have to figure out the clay side of it. Your clay will determine how hot you need to fire, etc. If I were you I'd start with the clay the locals use for their tourist wares. Just because they use it for tourist stuff doesn't mean it wouldn't work just fine for making pots or sculpture.

[Wyndham]

You need to learn what clay that's local can do. Some of the most beautiful ceramics are based on low (1800 deg f) clay bodies that are pit fired. Learn what the locals are doing, where they get their clay and how they prep it, then how they fire it. Just because it maybe tourist cr@#@#$p doesn't mean it's not good workable clay, though at a low temp.

Learn how they make their slip for decorating and what wood they use for the firing.

If you look up pit firing you'll see what beauty can be achieved in low temp ware.

After that you can develop your own expression in clay and there maybe other clay beds that can go to higher temps.

Most of the world still uses low temp clay bodies for everyday uses and can be better than higher temp stoneware for certain uses.

Wyndham

[joff]

Thanks everybody for the good advice. I think I'm going to use propane to begin with because it's cheap and plentiful down here. I really like the electric design, but I'd need a decent variable transformer to regulate the temperature, whereas with gas I just need a valve.

I still need to monitor the temperature. Any advice on an inexpensive pyrometer?

[Mark C.]

e-bay

[Benzine]

Yeah, eBay does have a ton of cheap pyrometers. You are also going to want some pyrometric cones, to measure the heat work in the kiln...... I just realize, that I've learned so much from reading John's posts, that I should stop reposting it, because I'm worried he'll start charging me for class credit hours.

[joff]

How about this one?

http://www.ebay.com/itm/High-temperature-thermometer-Pyrometer-for-glass-kiln-ceramic-kiln-/110940895666?pt=LH_DefaultDomain_0&hash=item19d497b9b2

[joff]

Benzine, what does that mean the 'heat work'? How is the temperature not simply the temperature?

[Benzine]

Benzine, what does that mean the 'heat work'? How is the temperature not simply the temperature?

 

Temperature is simply the temperature, but only at that point in time.  A pyrometer simply measure how hot the kiln is, at that given moment.  However, when you are firing ceramics, you want to know how much heat, the ceramic items have absorbed over time, which is heat work.  

 

This is why ceramicists use Cones, when referring to the temperature in the kiln.  The pyrometric cones are designed to melt, after they have been exposed to so much heat work.

[neilestrick]

When you cook a pork roast, you can cook it at 350 degrees for an hour or 275 degrees for 4 hours. Either way you get a roast that's cooked to 170 degrees inside. The heat work is the same even though the temperatures were different. In a kiln, the temperature at which you achieve the heat work will primarily depend on how fast the kiln is heating up. Faster climb equals higher temperature to achieve the heat work.

[joff]

Ah. I think maybe that's a pretty fundamental distinction. It's the kind of thing that doesn't get spelled out on the internet at first glance and for a person in my position (isolated by geography) is sussed out with some difficulty.

 

This is why I appreciate a good forum and the people on them.

[joff]

Faster climb equals higher temperature to achieve the heat work.

Meaning the faster you heat up your kiln the hotter it needs to go to heat the pieces all the way through, yes? And then I suspect the rate at which you heat (the climb?) affects a myriad of variables in the finished piece. And that the interest/obsession over these virtually infinite variables is what makes the hobby so compelling.

 

Am I on the right track?

[Benzine]

If you like variables, then you are indeed looking into an appropriate subject.  That link I posted to the kiln firing is proof of that.  And if you start mixing your own glazes, there is even more of the same.

[neilestrick]

 

Faster climb equals higher temperature to achieve the heat work.

Meaning the faster you heat up your kiln the hotter it needs to go to heat the pieces all the way through, yes? And then I suspect the rate at which you heat (the climb?) affects a myriad of variables in the finished piece. And that the interest/obsession over these virtually infinite variables is what makes the hobby so compelling.

 

Am I on the right track?

 

 

You got it.

[Lockley]

A couple of thoughts on your project. 

one) Small propane furnaces / kilns are the least efficient way to fire  any thing.  For the temperature achieved the total BTU expense is inversely proportional to the volume heated per item.  As a means of experimenting with the local clay I rather doubt you will find it satisfactory.  Since you are a rural area you might find it better to experiment with wood/agricultural waste fired kilns.  I would not dismiss the local potters so casually.  In my experience with various crafts local knowledge will often trump academic knowledge. Making friends with local potters may teach you things about local conditions and materials that will speed you toward satisfactory results.

In addition my experience with small propane fired furnaces/kilns/forges, has shown that control problems increase as size decreases.

 

two) Commercial burners from companies like WARD Burners are by far the most practical way to build  a kiln. Failing that there is a resource for building burners that I have not seen listed here before.

 

Gas Burners for Forges, Furnaces & Kilns

 

by Michael Porter   copy right 2004

 

Published by SkipJack Press, Ocean Pines, MD  Library of Congress # 2003115257

 

The contents of this book will short cut a lot of errors and futile effort,  I wish it had been available 30 years ago.

It is possible to build a Kiln burner with very simple plumbing fixtures but making one with the necessary range of turn down (variation of BTU output ) is difficult and very difficult with out first class gas regulators.

 

You may want to read the extensive discussion of Kiln firing that appeared on this forum last week. 

Good Luck

Lockley

 

[Mark C.]

As far as thermo couples for gas kilns get one with protection tube like this one.

http://www.ebay.com/itm/High-temperature-thermometer-pyrometer-for-reducing-environment-gas-kiln-/200810725909

Mark

[JLowes]

If I may suggest some material to investigate, check out Simon Leach's raku kiln videos on YouTube:

http://www.youtube.com/results?search_query=simon+leach+raku+kiln

 

Also his conversion of an electric kiln:

http://www.youtube.com/results?search_query=simon+leach+kiln+conversion

 

For one of his raku kilns, and the electric conversion he uses a cheap commercial propane weed burner.  I fire my propane raku kiln using the same burner, so I know it works, but not as efficiently as a venturi burner, nor with as much control.

 

The pyrometer on Ebay you posted looks like it would work; it has enough range for low and middle firing.  If you follow the link for the Type K probe there is a recommendation for getting a ceramic sleeve for reducing atmospheres.  You would need that also.

 

There is valuable information in the Leach videos, even if you decide to go another route.  Also, it would be helpful to know the characteristics of the refractory brick you have available.  I have seen a gas kiln constructed of house brick with a insulating fire brick base and insulating fiber interior, so many things are possible "in the bush".

 

You have an interesting project.

 

John

[neilestrick]

The big problem with having a weed burner raku kiln as your only kiln is that bisque firing can be difficult. Whatever you do, you'll need to be able to heat slowly at the low end for the bisque firing.

 

I think the big question here, that hasn't yet been answered, is: What kind of pots do you want to make? Do you want to make glazed functional ware, pots that are strictly decorative, or ceramic sculpture? This is what will determine what type of kiln will best suit your needs.

[Chilly]

When you cook a pork roast, you can cook it at 350 degrees for an hour or 275 degrees for 4 hours. Either way you get a roast that's cooked to 170 degrees inside. The heat work is the same even though the temperatures were different. In a kiln, the temperature at which you achieve the heat work will primarily depend on how fast the kiln is heating up. Faster climb equals higher temperature to achieve the heat work.

I like the roast pork analogy.  I usually use baking to explain the difference between transfer, earthenware glaze, bisque and stoneware firings.  Fruit cake, victoria sandwich cake, biscuits, roast potatoes. 

 

It always helps to compare with something that is familiar.  No doubt someone will come up with a "wine/alcohol" analogy............Babs?  

[joff]

(Edit- this refers to an earlier post about propane being inefficient, some other stuff came in in between... I should have quoted,)

Hmm... that's not really what I want to hear but I guess it makes sense. Still, I'm gonna call up my appliance repair guy and see what kind of burner he can come up with. It's the simplest, most readily available system to apply and control heat. When I know what I'm doing a bit better I might consider building an electric kiln.

I'm absolutely going to go out to the pottery village when I get a chance to see what they're working with and how they fire it. It's a ways away and I don't have a car so I have to intrigue someone.

I may well make my first attempt a wood fired pit/barrel thing.

I enlisted some drunken help today and got the wheel moved over to my house... it's Flintstone style. I guess that's appropriate for a noob... although I admit the first thing I did was think about where I could attach a motor and drive...

I went out back and tried to find some clay to practice with... long story short it didn't really work. I have found some chunks of very pristine light gray clay out there in the past, but what I ended up with today seemed more like dirt. It wouldn't stick to the wheel.

But the guy who loaned me the wheel is sure there are supplies in San Jose and he's going next week. So we'll see what comes of that.