Some of the key things you need when doing the process of glass fusing is a pyrometer. Pyrometer tells you the temperature of the air inside the kiln. Although it does not tell you the temperature of the glass, the air temperature gives you a general temperature of your glass.
Every kiln is different and unique. If you do not have a pyrometer, then it is a necessity to have a window so you can at least see what is happening inside the kiln. To purchase good quality kilns and glass fusing supplies, search over the internet.
A kiln shelf is not necessary to do glass fusing, but it is extremely helpful to have air circulating around your glass pieces. The circulating air helps to ensure that your glass is heating at an even temperature. Yes, you can fuse on the kiln bottom, but try to place your items on posts so that you achieve the needed air circulation around your piece.
kilns have a digital control knob. These are fantastic, but when using a digital knob, you have to be constantly observing your pieces to be sure to obtain the desired effect.
If teaching a class, or even for personal use a kiln sitter is a desired and sometimes necessary item. Also with a digital controller and no pyrometer, how can you decipher the temperature if you want to hold your glass?
It is important when purchasing a kiln that you spend your money wisely. Do your homework before you place an order for a kiln. Kilns are one of the most expensive items you will purchase when doing glass fusing.
Check out the different kilns and see what items are standard and what are added items. Be sure that your kiln comes with a pyrometer if nothing else. This is a key item when purchasing a kiln.