Fast Salts are always stored in a cool dry place because they very sensitive to heat and moisture. If the salts are exposed to light, decomposition takes place.
General Method For Dissolving Fast Salt :
Fast salts are freely soluble in water. The method of dissolving is as follows :
The Fast Salt (1 kg. ) is pasted with little water and further quantity of water (5 liters) is added maintaining the temperature at 30ºC. In the case of Fast Red B Salt the powder is sprinkled slowly on water stirring. It is kept for 5-10 minutes and filtered through a fine mulmul cloth.
Special additions are necessary in the following cases :
Fast Garnet GBC Salt requires a large proporation of water than above mentioned quantity.
In the case of Fast Blue B Salt (1 kg.) special addition of sodium bicarbonate (o.4 kg.) is necessary in the developing bath.
Sodium acetate crystals (0.2 kg.) are added in the solution of Fast Scarlet G Salt (1 kg.)
In the case of napthol AS-G combinations, the following special addition of acetic acid (50%) is made in the developing bath.
3.5 ml. per litre in case of open-beck method.
22.5 ml. in starting bath and 11.0 ml. in feeding bath in the case of tub-dip method.
General Method For Dissolving Fast Salt :
The dyeing process consists of two stages. In the first stage, the material is impregnated with napthol solution and in the second stage it is developed with a diazotised fast base or Fast Salt solution. The later combines chemically with napthol 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 ect. These involve the use of different material to liquor ratio and therefore different concentration of the dyestuff is used to get the same shade.
PROPERTIES
22.5 ml. in starting bath and 11.0 ml. in feeding bath in the case of tub-dip method.
These products are sparingly water soluble to completely water insoluble diazo components to which simple water soluble diluents are added.