Paint manufacturers use Bag Filters or Resin Bonded Cartridges for contaminant removal. Bag Filters are generally used for filtering thicker paints.
A range of micron sizes from 5µm to 400µm are used depending on how contaminated the paint is with lumps, gels, or particulate. Filtration is often located on the filling lines before the paint is packaged.
Filtering inks when filling ink cartridges for printers (a mixture of solvents, pigments, dyes and resins) requires the removal of particulate under 10µm to protect the dispersion nozzles on the printer from blocking.
The majority of ink cartridge producers use Polypropylene or Glass Fibre Pleated Filters. Absolute rated filtration at either 0.45µm or 1µm is preferred to give an excellent finish.
Inks for pens is filtered to produce a quality finish when writing.
Litho printers use plate technology and Reverse Osmosis Systems are used to produce pure RO water for plate rinsing. For further purity, DI water is produced. This ensures consistency and quality for each print run.
DI water is used to both 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 (Calcium) 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 is pulled through the cartridge using a vacuum. Typically this water is bought in but some manufacturers produce their own to reduce costs. Some printers filter the ink before use especially in high value applications, such as high quality publications.