Home Made Electric Glass Fusing Kiln




About: I am an electronics engineer working in telecommunications in the UK. Generally I work on chip design for digital radio receivers. I like all things arty and consider chip design a bit arty :) Basically I...

Intro: Home Made Electric Glass Fusing Kiln

Good evening anyone interested,

My name is Dave and I am from Bristol in the UK. Before Christmas I was out shopping in a market with my daughter Ava (8 yrs old) when she spotted some fused glass jewellery on a stand. Ava thought it was fantastic and immediately wanted to know if it was possible for her to make some. Obviously, I said yes without thinking as we make lots of interesting and arty stuff together. Once home I looked into the subject and realised we were going to need some type of Kiln to fuse the glass. I looked into the cost of a kiln and to be honest found the prices quite offensive so we (Ava & me) decided the way forward was to build a glass fusing kiln from scratch.

The first issue was an enclosure - luckily this was solved by my work. They were dumping a large aluminium radio test enclosure which seemed perfect. The enclosure already had an aluminium control box on the side and was generally very robust. The enclosure didn't have a lid but was otherwise good. I did some reading around and decided early on to heat the kiln from the top as this gives the glass a better gloss finish. So I knew from day one I was going to have to fabricate a top lid with integrated heating system. To fuse glass you need a sustained temperature of about 800C and aluminium melts at about 660C - so a small problem existed. The enclosure was going to have to be very well insulated and to achieve this I used a combination of ceramic fire brick, ceramic blanket and high temperature adhesive. To fuse glass you don't just turn on the heat full power and sit back. You have to increase the temperature slowly and more importantly reduce the temperature slowly to prevent thermal shock of the glass. To control this process I used an Altec PC 410 multi-program multi-step industrial temperature controller connected to a K-type thermocouple.

I hope you enjoy the series of videos and images I have included to describe my Kiln building project. Please if anyone has any questions or comments please feel free to get in touch and I will be more than happy to try and help.

Please remember if you attempt to build any type of kiln the resulting temperatures can be extremely dangerous and could result in serious injury. Not to mention the use of mains electricity in high current applications.

Step 1: Initial Look at the Enclosure & Temperature Controller

I have link to a video here which show the enclosure before I started to line it with insulation and also a look at the Altec PC 410 industrial heating controller.
My initial though was to line the enclosure with large bricks. However, these subsequently became difficult and expensive to get hold of. I found a supplier of standard size ceramic insulation bricks in Bristol and the guy did me a great deal with all the bricks and high temperature adhesive coming to under £100 cash - bargain !

(All the bricks, fire blanket and adhesive obtained from Paul at Complete Fire Protection (CFP) Bristol)

Video of initial look at enclosure and temperature controller :

Step 2: Enclosure Now Lined With Brick & Fire Blanket ...

After getting my hands on the ceramic fire insulation brick and ceramic fire blanket I set about lining the lower half of the box. So the box is initially lines with the blanket and then subsequently lined with the brick.

In order to make as much space as possible I cut the bricks down from the stock depth of 75mm to 50mm. The bricks can be cut using a standard hand saw. Do this outside as they create a massive amount of dust while cutting and I am sure you don't want to be breathing the dust. I made a simple wooden jig (see video) to get all the brick a consistent depth.

The bricks and blanket are all secured in place using a high temperature adhesive.

Video of lines enclosure :

Step 3: Construction of the Control Box

This section again features a video showing the completed control box that will drive the heating element.

Essentially the control box consists of the Altec temperature controller driven with a K-type thermocouple. The Altec then drives a 40A solid state relay which switches power to the heating element.

I have not added too many words here because I think the video covers things :

Step 4: The Construction of the Enclosure Lid

One of the most challenging aspects of building the kiln was construction of the lid section. I decided early on I wanted the heating element in the lid as this apparently would produce the best finish for the glass.

I decided to make the lid insulation from an array of the same ceramic fire brick used to line the lower enclosure. In order to hold everything together I went to a local metal supplier and got them to make me four corner brackets plus to long and two short straight sections and also cut a thin stop plate. The brackets and straight section were all cut from 2mm mild steel and the top plate from 1mm mild steel. The corner brackets and straight sections I drilled and screwed together around the brick secured with self thread cutting screws. The resultant lid is very sturdy if not a little on the heavy side. I also fitted a handle to the front which luckily came attached to the original enclosure obtained from work.

Step 5: Choice of Heater and Mistakes Made

Ok, so now I had a fire brick lid all held together with mild steel and a handle - what I needed now was a heater. Having looked at commercial kilns I decided I needed a heater capable of delivering about 2.5KW of heat. Quite a few of kilns I had looked at used an inexpensive heating element which is essentially a coil of resistive wire which is rated at a give power at a given voltage. The element I initially chose was rated at 2.5KW at 220V AC (see the image attached).

I ordered the heater from China and it was <£5 .....

The heater looked good on arrival and I proceeded to chase out a channel in the fire brick lid with a Dremel and an abrasive tool. If you are going to chase out this ceramic brick DO NOT use a fluted metal cutting bit the brick although soft will blunt the cutting tool in about two minutes rendering useless - I found out the hard way. Use an abrasive grinding bit which works really well. The element was pinned into place using pins made from a slightly thicker version of the same resistive wire - so just about 2cm of wire with a short ninety degree bend at one end.

So I installed the element with feed wires through the lid to the top side. I plonked the lid onto the lower enclosure and connected it directly to the mains.

Sure enough the element heated up to a cherry red hot and the temperature measured by the thermocouple started to rise.

OK - two major problems became apparent :

1. No matter how much you pin the element in place it expands a great deal when it heats up. The element then sags as large hanging loops under the force of gravity. In my case the loops were hanging down some 15cm into the lower enclosure and even when the power is removed and the heater cools the heater only contracts slightly leaving the loops to flap about - it just didn't feel right to me and I wasn't happy with the heater solution.

2. The heater caused the chamber to climb rapidly in temperature until it reached about 300C where the rate of increase slowed. By about 550C the temperature was rising painfully slowly at maybe 1C/minute and was clearly not going to reach 800C in any sort of reasonable time. At this point I had taken delivery of a mains power meter. Attaching the power meter showed my heating element was actually only delivering about 1.2KW and NOT the specified 2.5KW as the supplier had stated ! I think the supplier was just selling 'an' element as various powers hoping that someone didn't check - well I did, complained and got a full refund :)

So the bottom line was I decided to ditch the first heating element and rethink the entire heating problem.

Step 6: Final Choice of Heater and Lid Construction

After ditching the first heating element I set about looking for another solution. After lots of research and surfing I picked up another bargain but this time it was a winner !

I found a supplier selling 400W 240V bar style heating elements. These still use a coil of resistive wire but contained within a high temperature glass tube and capped off with ceramic end caps with screw bolt style terminals. I picked up ten elements brand new and boxed for £13 (the lot) delivered from the UK - happy days ! After the low power issue with the first element the first thing I did was pop one of the new elements on the power meter and was happy to get a reading of ~426W.

The plan was to stack eight elements in parallel to give a total power of ~3.2KW

I used two sections of 25mm steel angle iron to support the eight elements. Steel is not a very good conductor of electricity and even worse when hot. So I faced the steel angle with 10mm strips of copper plate to act as bus bars to conduct power efficiently to the heating elements. Each bus bar is then connected up through the lid using 2.5mm copper wire terminated with a ceramic connector block.

To fuse glass you need a temperature of about 800C and copper melts at 1085C. So I figured even if the top of the enclosure was 100-150C hotter than the temperature probe as long as I didn't go any hotter than about 850C the copper would be fine - this has proved to be the case with no issues to report.

Step 7: Finished Kiln and Some Temperature Data

Without adding too many words here is a short video showing the finished Kiln :

The lid is now attached with rear hinges and the heater has been fitted. The underside of the lid has been lined with more ceramic fire blanket mainly to stop metal oxide from falling into the glass chamber during heating.

The Altec temperature controller has an automatic tuning mode which learns the characteristics of the chamber and then automatically updates the control loop PIC parameters. This worked extremely well and after calibration the temperature matches the set point to within +/-1C and even when the sequence is put into hold mode the temperature only overshoots by 1C for about ten seconds - very impressive I thought.

Step 8: Temperature Results From the Kiln

One of the first things I did was to run the kiln at full power and record the temperature at one minute intervals up to 820C and then kill the power and measure the natural fall in temperature again at one minute intervals.

I then plotted the results - this data allows me to work out the maximum rate of heating / cooling at any point on the firing sequence to subsequently optimise the design of the glass firing sequence programmed into the Altec PID controller.

Step 9: First Result From the Kiln .....

Here is the first result from the kiln .....

The pendant on the left came from the microwave kiln I had been using and the pendant on the right from the new traditional kiln which has been the subject of this article.

The right hand pendant show much better shape, colour and no trapped air bubbles :)

Step 10: Conclusion .....

I have had a lot of fun building this kiln and have learned many new skills.

I realise that there is not a huge amount of construction detail in this article so if anyone has got this far and wants to know more about any aspect of the project please feel free to contact me.

One piece of advice I will give ....... when a top loading kiln is at 820C DON'T lift the lid and shove your head in to have a look at the work inside - bad idea, just a thought !

5 People Made This Project!


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77 Discussions


Question 23 days ago on Introduction

Hi Dave, great kiln you have made for your daughter.

I have been Glass fusing for about 10 years now using an old ceramic kiln with a glass controller fitted. We have now made our own kiln using a stainless steel case we had made by a friend and my son an electrician has fitted elements to the lid, supplied by midland elements and lined the kiln with superwool fibre board 50mm thick, we are using the sentry express controller from the old kiln.

it’s only been put in situ today but not commissioned yet.and we are a bit concerned about the weight of the lid. We plan on fitting heavy duty gas struts but although a lot of commercial kilns have gas struts fitted we are a bit concerned, that the heat might make the lid lift. Do you know if they use different gas struts on commercial kilns ?



2 more answers

Answer 15 days ago

Thank you Dave
We have the kiln running now it was a bit scary on the first fire with the binders burning off,black smoke and soot but its gone now after a couple of test fires
It seems to be getting pretty hot outside though we clamped the lid tight last night and it still got hot
Waiting to fit some latches to hold the lid down and get a tighter close,maybe that will help
Thanks for the reply I’ll see how hot it gets once it’s closed tight


Answer 15 days ago

Hello Lesley,

Sorry for the delay, I was on holiday.

I think standard gas struts would be fine. The outside temperature of my kiln to the sides is only about 70C and even on the top only hits about 120C. I doubt there are
special struts used on kilns for home use.

Let me know how you get on.




Question 3 months ago on Step 3

Hi Dave, awesome inscrutable! Im going to attempt to upgrade my small gas kiln in a couple weeks, and I had a question about the voltage. If im running this off a 120v, 15A outlet instead, which internal pieces would I need to change in order to run it without electrical issues. My element will be different, and requires 12A... is the initial breaker switch the only thing that has to change? Any advice is much appreciated.

1 more answer

Answer 3 months ago


If you are running from a 120v outlet rated at 15A you will only be able to a total power of approximately (120 x 15) = 1800w. If you want to support more power than this you will need multiple power outlets. The internal breaker I used was rated at 20A. This was to protect against a malfunction or short circuit. The current 20A breaker should be ok for your 15A outlet. I think the main issue is whether you have enough available power to generate the heating required. How big is your kiln going to be ?




5 months ago

Hello jlcurve,

Nice work !

I was planning on writing a C# GUI to control the Altec but never got around to it. I generally found that once I had my favourite firing profiles set up I didn't really change anything. However, having the temperature curve per firing would have been nice. I will take a look at your interface.

Maybe you should do a quite Instructable ?




Tip 5 months ago

Hi! Very nice construction!

I use the same controller for a ceramic Kiln. I wanted to log the temperatures but do not want to use the official software (I don't do windows), so I made a very simple console application to interface the Altec. You can also change most parameters without using the front panel interface. It needs a bit of polishing but I use it to obtain a realtime graph of every firing.





7 months ago

congratulations for ur kiln. can you tell me about the internal and external measures please?

1 reply

Reply 7 months ago


Yes, the dimensions are:

External: 51cm(L) x 38cm(W) x 46cm(H)

Internal: 36cm(L) x 23cm(W) x 22cm(H)




2 years ago

hello I made glass fusing machine big size 1250x1000x600mm for fusing glass basin. it didn't work could you help me I will send pictures

2 replies

Reply 10 months ago

Hi yonasjob, I am designing a similar size of your kiln project.Can you update on how you eventually made the project work. If you want you can write me to ogbmartso@gmail.com


Reply 2 years ago

Hi yonasjob,

Sure I will help if I can, please send some pictures .....


11 months ago

I know this is a basic question.... but what are the exact names of all the toggle switches u have ? or any links would help :) im trying to buy the exact same ones

thanks much


Reply 11 months ago

Hello oki-piovera,

I have taken a look at the controller you are interested in. I DO NOT think this controller is ideal for a fused glass kiln design. The controller in question appears to only be able to control one temperature and seems to be targeted more towards pottery kilns. When glass fusing the temperature must be increased at a controlled rate across multiple set points. Similarly the temperature must also be reduced at a controlled rate. Therefore, the controller used must be capable of multiple process steps (generally 8-10) and also programmable rates between steps.

Hope that makes sense, please fire away if you have questions ...


Reply 11 months ago

Ok, thank u for the response. I think im going to buy the pc410. Im making a smaller kiln for making enamel on copper / silver watch dials. If possible can you email me your email address ? I can donate or send you a gift for answering any questions i have.. :) thanks much oki-piovera@mail.com


1 year ago

What terminals did you use for the heating elements?

3 replies

Reply 1 year ago

The heating elements I used had bolt terminals at each end complete with a nut and washer (see step 6). I fabricated two steel angle bus bars. Steel is not a particularly good conductor of electricity especially at temperature so I faced the steel bus bars in copper plate (melting point 1085C. The bus bars were then bolted into the firebrick lid, the bolts being seated into holes in the firebrick filled with high temperature adhesive. The same adhesive used to bond the firebricks together - hope that makes sense ?


Reply 1 year ago

That makes sense, except that the ones that i found (since the ones you referenced were no longer available) do not have the same terminals as yours. These are the ones that i found but without the terminals (i think): http://www.ebay.co.uk/itm/4x-400W-Halogen-Heater-Replacement-Tubes-195mm-Fire-Bar-Heater-Lamp-Element-Bulb-/331567729860?hash=item4d32fa0cc4:g:oFwAAOSwNSxVZvWN
Anyway, thanks for replying quickly. idk if these will work. Let me know if the don't.


Reply 1 year ago

Hi, yes I have some of the same elements. They will work fine in terms of heating the kiln. The only thing that needs addressing is how to mount the elements. The elements you have clip into a ceramic spring loaded holder with a connecting wire. The ceramic holder will probably be up to the 800C+ at the top of the kiln but the wiring (outer coating) will probably break down. So you need to make sire the wiring is protected either by running it inside the brick or by surrounding the inner wire in ceramic sleeving. You can buy ceramic sleeve on ebay. I used the sleeve to run the copper connecting wires out of the lid and into the small terminal box on the top of the kiln lid. The ceramic sleeve prevents the copper wire shorting with the metal lid or terminal box.