Instructables
Picture of Homemade Electric Kiln
13, 3:08 PM.jpg
I was frustrated with the price of electric burnout kilns for ceramics, metal annealing, glass enameling, and melting precious metals etc,. so I decided to build my own. Most kilns that run at these temperatures cost between $600 and $1200. With a little help from a guy at a ceramics store, I built one for about $120 (not including the power controller and pyrometer). This little electric kiln can get up to 2000 degrees F and is easy to make without any special tools besides a handheld router. I also wanted one that I could take apart and replace the element, since these are inexpensive.

Materials:
1. 8 x 10" bolts with nuts- 1/4" diameter
2. 7 x soft fire bricks (4 1/2" x 9"- make sure they are soft)
3. About 7 feet of angle iron from Home Depot (this is the frame) (4 x 14" legs/corners, 2 x 9" floor supports)
4. One sheet of thin aluminum (for the door). At least a 9" by 9" square
5. One 1/4 inch x 26" coiled heating element (stretched to 29 1/2")
6. One small hinge with screws
7. Fire proof pins (should come with element)
8. Short outdoor extension cord rated to at least 10 amps (cut down to 3 feet)
9. Variable controller-I've seen them on ebay for $20 rated at 15 amps
10. 1" thick Kaowool- about 1 foot square

Tools:
1. Hand held router with 1/4 inch bit
2. Wrench
3. Needlenose pliers
4. Hacksaw
5. Wire cutters/stripper
6. Drill
7. Tin snips
 
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Step 1: Cutting the channels

Picture of Cutting the channels
1. Pencil the channels in as a u-shape 1/4 inch wide. I left about an inch, to an inch and a half from the edge and the top of the "U" so the elements are not too close to the opening of the kiln.
2. Route out the channels with your router using a 1/4 inch bit.
3. You will need to cut one of your fire bricks down to a square 4 1/2" by 4 1/2" for the back and route out two straight channels. This will be the back wall.
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RobBBorger8 months ago
This is great!! Simple and functional. And very well explained, I have no doubt I can make this with your instructions. Thank you so much, I would never be able to afford one otherwise.
altomic11 months ago
awesome. i want to make so I can blow glass. wondering how I could do it and bam -your instructable. thanks.
rwlarkins11 months ago
Terrific!!. I have been trying to find an inexpensive kiln for copper enameling for years. Never could afford a store-bought one. Thanks. This appears to be fairly easy to build.

Robert Larkins
Jugfet11 months ago
An excellent project and so simple!
I'll be assembling one of these soon for smelting Tin (Sn) ore.
Wolfgar77 (author)  Jugfet11 months ago
Thanks!
Thanks! I have been wanting to make -- not a high temp kiln, but a low temp oven for polymer clays, and this instructible gave me insight on how to construct it.
mssadnblue11 months ago
Thank you so much for showing how to make a kiln! I have been wanting one forever but where I live they usually run $1500 and up -- way out of my budget. Now I will be able to build my own at a much more affordable price. Thanks!
Wolfgar77 (author)  mssadnblue11 months ago
You are more than welcome. I was in the same boat! Necessity is the mother of invention.
Awesome Ible!!!

Expensive store bought kilns have the same problem with the elements popping out - they heat up, expand, and voila, out they pop! (so don't take it personally!)
My paragon kilns have metal staples that hold the elements into the channels - they often come loose and need to be pushed back in, I believe they're just steel - would that work?

Also, for around your door - perhaps a woodstove gasket would work? I've used it instead of foil as a gasket, works great, cheap as hell.

Either way, nice job. Looks a helluva lot nicer than my waffle iron kiln!
Wolfgar77 (author)  bonecholampworks11 months ago
Thanks- your waffle iron kiln is a great idea and one of the first ones I looked at before building this. I almost built your waffle iron kiln but for some of my projects I was afraid it might be too small. Thanks for some of my original inspiration!
ssbk233 months ago

Great presentation. Could you be a bit more specific about the controller?

A link would help a lot understanding what to purchase.

Thank you.

dev0703 months ago

Hi, thank you for the great write up. I don't know much about electronics, what should I consider when purchasing a controller? I see a lot of "Variable speed" controllers. Will those work? Also, thank you for warning me about plugging it directly into the wall, what ill effects will that have?

Wolfgar77 (author)  dev0703 months ago

I am not an expert in this area. I was lucky and had a controller from an old kiln. The variable speed controller should work as long as the amperage rating is high enough to carry the load. I would think 15 A is what you houshold circuit is rated as well. The controller we list in the link in the comments below should work. I would not plug it directly into the walk socket for two reasons. 1. It could spark and you increase a shock hazard when you do this 2. You have no way to control the heat and the coil will heat up to the maximum temperature until you unplug it or the coil burns out. Really though, you do these projects at your own risk, so continue to ask questions from people around you.

Deeg10 months ago
What are you using for a power supply? What is the voltage and wattage? Is it DC?
Wolfgar77 (author)  Deeg10 months ago
Hi Deeg- the power supply is one I pulled from my old kiln and it doesn't have any markings on it. It is an AC unit though, with a outlet in the back. It is really more of a variable controller that plugs into any 120 outlet. I'm sure something like this would work http://www.ebay.com/itm/AC-ELECTRONIC-VARIABLE-SPEED-CONTROL-UNIT-FOR-POWER-TOOL-ROUTER-POTENTIOMETER-/250921201822?pt=LH_DefaultDomain_0&hash=item3a6c11b09e - hope that helps

hi, perhaps i'm asking an obvious question but are you accually using a kind of variable resistor directly in line with a live power outlet and not a separate powersupply?

No fuses or anything?

Wolfgar77 (author)  kjohansson13 months ago

the simple answer is yes.

I got the same one from Harbor Freight a while ago too, works perfect.

http://www.harborfreight.com/router-speed-control-...

Droster4 months ago

Awesome! Suggestions on the heating element?

Wolfgar77 (author)  Droster4 months ago

Hi Droster- read the comments below. I think we cover that. Mine is a NiCr wire. I wound my most recent one to about 24 inches then I stretched it to the 29 inches I needed.

Droster Wolfgar774 months ago

Ahhh, oh yah, there it is, slipped right past my eyeballs. Thanks!

mcelroy95026 months ago

So when you say use soft firebricks, i dunno what that means in terms of firebricks. Do you know what brand are soft firebricks?

Wolfgar77 (author)  mcelroy95025 months ago

they are just called "soft insulting fire bricks". You can get them in different sizes. Here's link to help you out. http://www.sheffield-pottery.com/SOFT-BRICKS-Insulating-Firebrick-s/372.htm

thanx, appreciate it

ecircusitch6 months ago

In step 5 you say,

"**Safety tip--Do Not plug this directly to a wall outlet."

What happens if we do? Is it like crossing the beams in Ghostbusters?

Wolfgar77 (author)  ecircusitch5 months ago

Well, it could spark "stoping every molecule in your body" and cause a total universal implosion. What will probably happen is heat up your coils to their max capacity, if run for a long time it could burn out the coils. Safer to regulate the power and have an on/ off switch.

carly97 months ago

This is awesome! I have been searching the internet trying to find something like this. Does this kiln take a lot of energy to power though? Also, do you think this design could be tweaked to make a fire kiln?

marcoval7 months ago

I live in a small town so my efforts to build this will be limited to purcahses on the net. Can you give some ideas on the best ways to get this stuff, specifically the coil? I've found this one but it seems too long. Also how difficult is this to stretch myself?

http://www.aberdeenhomerepair.com/store/p1891.php

Gracekelly31210 months ago
What are the dimensions inside of the finished kiln?
Wolfgar77 (author)  Gracekelly3128 months ago

4 1/2 inch high by 4 1/2 ich wide by 6 1/2 inch long

About time someone found a way around buying test kilns.
Vidar_7610 months ago
Nicely done!

I got i bit curious about your router. What kind is it?
Wolfgar77 (author)  Vidar_7610 months ago
The router is just a handheld Ryobi router I bought at Home Depot. Battery operated.
Vidar_76 Wolfgar7710 months ago
Ok, thanks!
EugeneNDixon11 months ago
Elements must be for ceramic use, they are made from a material called "Kanthal"
Ni Chrome wire will not take heat. To prolong life of elements limit exposure to air
when firing kiln.
Wolfgar77 (author)  EugeneNDixon11 months ago
NiCr can be used but but you are right that kanthal is probably a better choice. I don' t know what mine is because it was wound for me and I didn't ask that question. Silicone carbide or molybdenum disilicide can be use for higher temperatures. I still advise anyone building one to go in and talk to someone more knowledgable than me and get an element that will work for your application. If you don' have a ceramics supplier in your area, call or go online to Joppaglass.com. I checked out their site and their elements are very reasonable and you can get an element for the application you want. I told my guy that I had to have one that goes to 2100 F and that's what he wound for me. We also worked out approx how long it should be and what power supply I was using. All these factor in.
Wolfgar77 (author)  Wolfgar7710 months ago
I just talked to my ceramic experts today- all of these elements for ceramics are NiCr but the company that produces much of the wire is called "Kanthal". Learn something new everyday!
This is a material error, EugeneNDixon. Not only does NiChrome wire take the heat, it was specifically designed in order to do just that. Another alternative wiring source is purchasing Rewiring Furnace Kits from suppliers like Johnson (I order mine from my local hardware store) Check for L36-953.

It is important to know the total length in groove inches, plus both straight lengths for attaching to the power (+ and - ), and the resistance of any wire/element, plus the amperage you plan to draw in order to re-wire your own unit. I recommend keeping the amperage between 10A and 11A to reduce the "popping the breaker" surge when powering up the furnace.

I rewire and rework mine whenever it needs it. Furthermore, use excess wire to wrap a short length around the tip of a pair of needlenose pliers, in a U shape. This will make one's own "staples" for holding coil into the brick. Never have a shortage of "staples again" nor worry about sliding out of the routered groove with your own DIY "staples."

Hope this helps someone, regardless of end purpose of the furnace - kiln.
Breygon11 months ago
great ible. do you know if it can be scaled up for a larger piece I.e. 1 ft cubed or would it require another element or two?
Wolfgar77 (author)  Breygon11 months ago
I have thought about that. I suppose it could but you would have to figure out how to support the floor and in instead of bolts to hold it together you would need something longer. I don't have welding equipment and all the bigger kilns needed sturdier frames. The bigger kilns mostly use the hard fire brick which you cannot route and that creates another problem to be solved. Lastly, the power tolerances would be different using two elements, so the draw would be greater. Most larger kilns run on 240V and much higher amperage. Again, this might be a question for someone who builds kilns for a living.
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