One of the main use of thickeners is in the paint and printing industries, which depend heavily on rheology modifiers, to prevent pigments settling to the bottom of the can, yielding inconsistent results. Water based formulas would be nearly impossible with the exception of India ink and the few other water soluble pigments, but these would have very little coverage and at best would stain wood slightly. All modern paints and inks will have some pigment added at the factory for opacity and to control the specularity of the finish, from matte to high gloss, dependent on thickener used, but more so on the size of the particles added as opacity modifier. One-micrometer (µm) particle sizes and below will be the limit of high gloss, probably confined to luxury automotive coatings, and about 100 µm particulates will make a bumpy surface on the microscopic scale, which scatters light and makes the surface appear matte.