Naphthol dyestuff have traditionally been applied by the multi stage route of impregnation, hydro extraction/rinsing and development.
German and Swiss manufacturers have now developed a one bath application process which offers a real rationalization of the dyeing process. This one bath process is cotton in hank in open becks and spray dyeing units and cotton piece on the winch.
The basis of the method is to retain the bath after impregnation and maintain the color pigment which is formed during development in highly dispersed form, by means of a special auxiliary. The one bath method consist of
- impregnation for about 20 minutes. at 20 to 30°C.
- addition of acid and dizao solution without letting off the bath.
- coupling the dyestuff of about 30 minutes
- cleansing after treatment.
A fairly wide selection of naphthol/base combinations are suitable for this process.