There are many different artistic techniques for working with glass, from traditional leaded work and copper-foiling (like Tiffany lampshades) to glass blowing and lampworking (making glass beads). Fused glass (or kiln-formed glass/warm glass as it also referred to) is another of those techniques, and is a process that uses a kiln to manipulate heated glass to achieve the desired effect. It is fused glass that I specialist in here at MooniGooni Glass.
For fused glass techniques, generally different pieces of glass are stacked together and heated in the kiln to form the design. The temperature used to 'fire' the glass dictates how the glass will look when it eventually comes out of the kiln. The higher the termperature the more molten the glass becomes, and the more it 'flows' and becomes smooth and rounded at the edges. At lower temperatures there is less flow of the glass, but these temperatures are good for shaping/bending the glass over and into moulds to achieve a desired shape. And there are, of course, a whole range of temperatures in between that can be used to gain many other different effects!
Different materials can be used in between and/or on top of the glass prior to firing, including: metals, oxides, powdered glass, ground glass, enamel paints. Some of these inclusions react with the chemical compounds in the glass when they are fired together and can produce really interesting artistic effects ie: silver foil reacts with the sulphur/selenium bearing glass and gives a yellow/brown/dark reaction on the glass. You can see some of these reactions on various pieces of work on the website, in particular some of the trinket bowls.
Glass is a fab medium to work with and is extremely versatile, but it can be a fickle friend too! I like to refer to those projects as 'happy accidents' (a la Bob Ross!)