Homemade Electric Kiln

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Introduction: Homemade Electric Kiln

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 insulating fire bricks (4 1/2" x 9" x 2 1/2"- 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 3/8 inch x 19" coiled heating element (stretched to about 28") out of 16 gauge Kanthal wire. I had this wound for me at the local ceramics store. I recommend you wind your own or as a ceramic supplier in your area to wind one for you. In my other instructable, Electric Kiln -Top Loader, I give directions on how to wind your own.
6. One small hinge with screws
7. Fire proof pins (should come with element) or you can make these out of the Kanthal wire.
8. Short outdoor extension cord rated to at least 10 amps (cut down to about 6 feet)
9. Stand alone ICS kiln controller. Sundanceglass.com has one for $84.
10. 1" thick Kaowool- about 1 foot square

Tools:
1. Hand held router with 3/8 inch bit
2. Wrench
3. Needlenose pliers
4. Hacksaw
5. Wire cutters/stripper
6. Drill
7. Tin snips

Step 1: Cutting the Channels

1. Pencil the channels in as a u-shape 3/8 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 3/8 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.

Step 2: Putting in the Element

1. You'll need two bricks for the floor, as pictured.
2. The dimensions of the fire bricks are 4 1/2" x 9" x 2 1/2" - when you construct the firebrick box, the kiln will be too wide across (2 outside walls at 2 1/2" and your back wall is 4 1/2", for a total of 9 1/2"). To make the walls flush with the roof and floor (9") you will need to take out a 1/2". In the first pic you can see I shaved off a1/2" from the right side. Any saw can cut these bricks, they are very soft.
3. The element I started with was 24 inches long. Separate the coils of the element so that they aren't touching. If you are unsure of how to do this, then you can always ask the people at the ceramic store. This stretched my element out to 29 1/2 inches. My element cost me about $25.
4. You'll need to drill two holes out the back of the kiln so you can run the ends of the element out the back. These are drilled inside the top channel about 1" apart. Pick a drill bit slightly bigger than your element wire.
5. Thread the element into the channels as shown.
6. If the ceramics store gives you pins, I found it was better to use pliers and make little u-shaped pins out of them. You can push these into the fire brick about an inch apart to keep the elements in the channels. It doesn't seem important now, but when you start firing, the element will want to flex and move around. The pins will keep it fixed in the channels.
**update - There have been many questions about the element I used and where I purchased it. I had hoped people would ask questions from their local ceramics store and get answers there. That is where I had my element wound for me. I have learned a few things since then. The element is a type of NiCr wire called Kanthal. Most Kanthal is rated to about 2450 F. There are other element types if you need higher temperatures. Kanthal is used in low-fire/ceramic applications. Either find a ceramic supplier to help (as I did) or you can contact a place like Joppaglass.com and have an element made to your specifications. They will usually want to know the voltage of the power source, max amperage (my garage is 15 amp breaker) and the gauge of wire (I think mine is 16 gauge). The arbor (inside and outside diameter of the element) can be requested and you can get the element you want.

Step 3: Making the Frame.

1. The frame I designed, squeezes it all together. Cut four 14" lengths of the angle iron with your hacksaw for the corners.
2. Cut two 9" lengths for the bottom. These two pieces hold the floor and rest on two 10" bolts on the bottom.
3. Thread the bolts as shown--4 on top,4 on the bottom. Two of the bottom bolts hold up the floor, the rest just squeeze the whole project together to hold the bricks in place.
4. Remember to place two bricks on top for your roof. Also, you can see that I have the whole project off the floor by about 3 inches.
*Safety tip--never use this or any other kiln on a surface that isn't fireproof. I always have this on my concrete floor in the garage.

Step 4: Making the Door

1. With your tin snips, cut your aluminum sheet into the shape shown in the picture. The dimensions I used make a 6 inch door. The central square is 6" and the tabs are 1 1/2". (So start with square 9" by 9" and cut out the corners)

2. I used a sophisticated metal break to bend the metal (called my fingers and a scrap of wood). Bend the tabs up so you have 1/2" on the inside and the door itself is 1" thick.

3. Cut a 6" x 6" square of the 1" thick Kaowool and squeeze inside the metal as shown.

4. Attach the door with a small hinge. I pre-drilled some holes in the frame and used metal screws to screw it to the frame. I didn't put a latch on this. As an option you could by-pass this step and use another fire brick over the entrance.

Step 5: Connecting the Power

1. Cut an outdoor electrical cord(10 amp) down to 6 feet and keep the plug end. You don't want it too long.
2. Strip the wires and connect to the element wires coming out the back of the kiln. My element came with metal connectors and ceramic sleeves. The sleeves are optional. I have since used small bolts to attach the power. This separates the terminal wires from the copper wires of your power cord and the nuts and bolts act as a heat sink to keep your wires from getting too hot
3. You need to ground this by attaching the green wire to the frame. I just found a small metal screw and attached it to the frame.
4.
**update 1/5/2017: A lot of people have asked me about my green controller. This was from an old kiln and has no numbers or markings on it. I have done some research on the type of controller you will want. They are called stand alone ICS kiln controllers. I have found one at Sundanceglass.com (pic 2 and 3) and have ordered one for myself as a backup for my controller. This is an infinity switch which will turn the power off and on depending on the setting you use and will allow you to obtain an even temperature. Use a thermocouple and pyrometer to monitor your heat and then you will know what setting works for the temperature you are trying to reach. There are some people in the comments that have used PID controllers and they have Instructables on how to wire them up to your kiln. I think cost wise, it is about the same to order an ICS controller or a PID controller.

**Safety tip--Do Not plug this directly to a wall outlet. Also, do not touch the element wires when the kiln is on.


5. I ran a piece of flat iron across the back wall of the kiln so that the back wall has more stability. This is not essential. When I first made my kiln, the squeeze of the frame held the back wall in fine.

Step 6: Finished Kiln!

1. In the original incarnation of my kiln (1st pic) I drilled a hole in the top and mounted an old thermocouple/pyrometer on top of the kiln.
2. I have recently upgraded to a better thermocouple (Pic 2) and directly connected this to the analog temp. gauge on my controller. I was lucky and had one of these from an old kiln I broke. For accurate firing temperatures I recommend a K Type thermocouple with a digital pyrometer. Another option for ceramics or glass enameling would be to drill a viewing hole in the side and then buy a ceramic plug for it.
3. I have run this for many hours at various temperatures (3rd pic). I really have not experienced any problems except my element still wants to pop out of those channels. I"ll just have to keep an eye on them.

Please let me know what you think or questions you have.

**update Dec. 11 2014- I have run this kiln now for hundreds of hours (firing clay, PMC clay etc.) and found the max temperature to be 2300 F.

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173 Discussions

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.

awesome. i want to make so I can blow glass. wondering how I could do it and bam -your instructable. thanks.

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

An excellent project and so simple!
I'll be assembling one of these soon for smelting Tin (Sn) ore.

1 reply

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.

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!

1 reply

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!

1 reply

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!

0
user
Jamie9

7 months ago

You out to sell these! I would buy one!

1 reply

In muffle furnace, the test sample is kept
away from any other element that can affect the result of the test such
as fuel of combustion, ash from burning, the smoke of burning.

http://newmeditech.com/products/lab-equipments-products/muffle-furnace/

wolf; exciting challenge for me to get my kiln finished, but......

just wondering about the Kanthal coil. I must assume the coils overall length on my mandrel is 19 inches (not including the pigtails) correct? Also, as stated, the coil should be 3/8 inch, meaning the o.d. of the coil is 3/8"?

Thanks for your inspiring creativity!

1 reply

yes, to all of your questions. Just don't stretch it out too much when separating your coils or it will be too long. My outside diameter was a little bigger when I ended up making my own coil because my mandrel was 1/4" and the width of the wire pushed it up slightly over 3/8". I just filed my channels down a little and it fit fine. I think the last element I made was about 18 inches. You don't want to go much shorter than that or the kiln will heat up too fast with too little resistance. Please let me know if this helps and how your final kiln turns out!

Hello sir, I was wondering how much watts this furnace uses.

I am making a furnace myself and I can only use 1500-2000 watts due to my outlets having a max of 16A AND the group being connected to the living room and fridge.

So there are little amps left for me.

My furnace (Foundry) is 0.15 cubic feet, do you think this is enough to heat it up to Alluminium melting temperatures?

4 replies

Probably not. I'm not an electrician, but I have mine in the garage and I can barely run anything else on that circuit without tripping the breaker. On dedicated circuit you will have enough heat to melt aluminum though.

this furnace itself is overkill for an aluminium furnace. Honestly you could make one out of a steel bucket hair dryer plaster of Paris and sand and melt aluminium with charcoal or modify it to use propane. Trust me, that kind of furnace could melt steel if the coals are hot enough

yeah, well, tell me how well you can use metal clay, or glass enameling with that design and get back to me. This kiln has multiple applications besides melting aluminum.