Fast Salts are always stored in a cool dry place because they are very sensitive to heat and moisture. If the salts are exposed to light, decomposition takes place.
The Dyeing Process consists of two stages. In the first stage, the material is impregnated with naphthol solution and in the second stage it is developed with a diazotised fast base or Fast Salt solution. The later combines chemically with naphthol absorbed by the fibre to give an insoluble dye on the fibre.
Depending on the type of the equipment available different dyeing methods are used i.e. open beck, tub-dip, circulating liquor, jigger, padding methods etc. These involve the use of different material to liquor ratio and therefore different concentration of the dyestuff is used to get the same shade.