Aside from its main use in lacquers, small amounts of nigrosin are used for negative staining of bacteria. as well as the capsule-containing fungus Cryptococcus neoformans. The shapes and sizes of the organisms are seen as color-free outlines against the dark background.
The mentioned formulation is only one of the ways of preparing the dye solution. Depending on personal requests and standard laboratory operating procedures, the dye solution can be prepared according to other protocols.