Ceramic kilns are specifically made to hold much larger items than the glass kiln will usually cater for so using a ceramic kiln might prove extremely inefficient if you're intending to use it to fire smaller items like jewellery.
The first issue to look at for glass fusing kilns is size! Can you fit it in the home...can you even get it through the front door? Make sure you read the specs to check the outer dimensions and make sure to add on about 6-12 inches around it when it's set up as it'll get hot!
Check the size of the firing chamber. Smaller kilns, such as the Paragon SC2 are perfect for smaller items such as glass jewellery but are too small for larger items such as plates and candle arches for example.
The larger the kiln, the larger the power supply needed to run it. UK domestic power sockets can run upto about 13 amps so smaller to medium sized kilns such as the hotstart pro can be plugged directly into the wall. Larger kilns run from 30amps or more of power so require a breaker to be fitted by a qualified electrician to your fuse box. A line is then fed to the position of the kiln and a 'cooker type' switch is fitted with the lead for the kiln running directly to the switch. In order to qualify for insurance the work should be certified (check with your insurance provider about coverage).
Small to medium kilns will run an average firing for between 14p- 50p each with larger kiln averaging £1 plus per firing. Always ask the retailer for average running costs- they should already know them so you don't get a shock when you get your next power bill!
The next issue to look at when buying glass kilns is how the kiln opens and where the heating elements are. This is very important as some kilns will allow you to work inside the kiln when it's on, some won't and this is largely dependant on the position of the heating elements within the kiln.
Kilns are usually divided into two kinds- top loading or front opening.
If you want to be able to work inside the kiln when it's on- for example to make glass bracelets on a mandrel, you need a top loading kiln (such as a firebox) so you can get access. You must however make sure the heating elements aren't located in the lid of the kiln (for example hotstart pro) otherwise it's going to be very hazardous!
There are positives and negative to the positioning of the heating elements and everyone has differnet view depending on how they work but generally-
Heating elements located at the top of the kiln- provide more even heat and reduce the need for second firings. Some kiln work might be difficult though.
Heating elements located at the back of the kiln- will heat slightly unevenly so items placed nearer the element will have a more rounded appearance. This can be a bonus though, allowing you to produce several types of item in one firing. Some warm glass work, ie bracelet forming can be tricky though due to the uneven heating.
Heating elements located around the sides of the kiln- will generally heat evenly (usually with a slightly colder spot in the centre) and are great for warm glass kiln work.
Important things to look out for!
- Does the kiln have a pyrometer?- Essential to monitor the temps in the kiln.
- Does the kiln have a controller?- Not completely necessary for smaller kilns although strongly recommended as it'll enable you to program firing scheduals to suit as well as learn how to use the kiln effectively
- How much do it cost to run? Ask and average cost per firing.
- How large is the firing chamber?- You may be better off in the long run getting a larger kiln which can produce the same amount in one firing as a smaller kiln can in 5 firings.
- What are the outer dimensions of the kiln? Will it fit!...Remember to allow approximately 6-12 inches around the kiln as they do get hot (duh).
- What's the power req? Upto 13 amps is fine for domestic UK supply...more than 13 then consult an electrician.
Other than that, check the sellers credentials-make sure the kilns comes with a guarantee incase of faults and that you can ask questions about the kiln when you get it home.