There are several good books on glass fusing, I reccomend reading the Fused Glass Handbook by Gil Reynolds and also Kiln Firing Glass by Boyce Lundstom. I have been fusing for almost two years and I really do it by "feel". Once you see the result you want you will know the next time when to slow down the kiln etc. There is a small kiln by Paragon that is alot of fun to work with...it is excellant for making jewelry and experimenting. Buy one and have fun. I reccomend you use a controller with it so you can hold the kiln at a certain tempature for a period of time. In essence fusing is based on the correct combination of time and tempature.