Toner is a powder used in laser printers and photocopiers to form the printed text and images on the 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, and bind to the paper.

In earlier machines, toner was poured by the user from a bottle into a reservoir in the machine. Modern machines feed directly from a cartridge. Empty cartridges are sometimes refilled by third party vendors.

Composition, size and manufacture

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 melting point vary the most.

Originally, the particle size of toner averaged 14–16 micrometres or greater. To improve image resolution, particle size was reduced, eventually reaching about 8–10 μm for 600 dots per inch resolution. Further reductions in particle size producing further improvements in resolution are being developed through the application of new technologies such as Emulsion-Aggregation. Toner manufacturers maintain a quality control standard for particle size distribution in order to produce a powder suitable for use in their printers.

Toner has traditionally been made by compounding the ingredients and creating a slab which was broken or pelletized, then turned into a fine powder with a controlled particle size range by air jet milling. This process resulted in toner granules with varying sizes and jagged shapes. To get a finer print, some companies are using a chemical process to grow toner particles. This results in more uniform size and shapes of toner particles. The smaller, uniform shapes permit more accurate color reproduction and more efficient toner use.

Clean-up

Toner can be washed off skin and garments with cold water. Hot or warm water softens the toner, causing it to bond in place. Toner fused to skin eventually wears off, or can be partially removed using an abrasive hand cleaner. Toner fused to clothing usually cannot be removed.

Toner particles have electrostatic properties by design and can develop static-electric charges when they rub against other particles, objects, or the interiors of transport systems and vacuum hoses. Because of this and the small particle size, toner should not be vacuumed with a conventional home vacuum cleaner. Static discharge from charged toner particles can ignite dust in the vacuum cleaner bag or create a small explosion if sufficient toner is airborne. This may damage the vacuum cleaner or start a fire. Toner particles are so fine that they are poorly filtered by household vacuum cleaner filter bags and can blow through the vacuum motor or into the room.