The printers use a «dry» processing technique known as thermal dye transfer (as opposed to the traditional «wet» process of bathing exposed film in liquid chemicals). (scientificamerican.com)
It is one of a long list of liquid chemicals used to wash coal, and such chemical or physical washes are commonly applied to most mined materials, whether minerals or ores. (scientificamerican.com)
Ammonium hydroxide is a colorless liquid chemical solution. (mountsinai.org)