Litho printers use plate technology and reverse osmosis (RO) systems are used to produce pure RO water for rinsing the plate between uses. For further purity, deionised (DI) water is produced. This ensures consistency and quality for each print run. DI water is sometimes used to reduce the viscosity of some inks before printing and to clean equipment after printing. The high purity water is used to prevent any contaminants being added to the ink which could damage the final product and also to prevent contaminants such as hardness building up on printing equipment which again could damage/distort the final product.
DI water is also used to clean inkjet cartridges before re-filling. The DI water is warmed and then pulled through the cartridge using a vacuum. Typically, this water is bought in but some manufacturers produce their own to reduce costs.