Toner is a power used in laser printers and photocopiers to form the text and images on the printed paper. In its early form it was simply carbon powder. Then, to improve the quality of the printout the carbon was blended with a polymer. Toner particles are melted by the heat of the fuser, causing them to bond to the paper. The specific polymer used varies by manufacturer but can be a Styrene Acrylate Copolymer or a Polyester Resin. Toner formulations vary from manufacturer to manufacturer and even from machine to machine. Typically formulation, granule size and melt point vary the most.