Fourcault process the pit must be "heated back" and then the process can continue anew. Glass chemistry has a huge impact on the process since it controls the melting, forming and annealing temperatures, liquidus temperature (point where various chemicals that make up the glass start to crystallize out of the glass) and rates of change of characteristics of the glass itself. Occasionally the ribbon will break or crack, leading to failure of the drawing process. Such breaks, known as "checks" can be alleviated by using proper operating parameters. Sometimes an expedient measure, using a portable source of heat, can be used to
Photosensitive glass naked eye (i.e. gold or silver) are in the glass. These microscopic particles move and grow when heated to form the photographic image itself. The process is similar to camera film, however a "negative" is placed on top of the photosensitive glass and then exposed to ‘’’ultraviolet’’’ light. Camera film, of course, would be exposed to ordinary visible light. Then there is a special process for the exposed photosensitive glass. The glass is reheated then in a kiln and postbaked for several hours. The image then "appears" within the special exposed glass as if by magic. The heated piece of