Nepthol are insoluble azo dyes applied to cellulosic fibres by impregnation in a Nepthol solution and subsequent coupling with a colour salt. All cellulosic fibres such as cotton, linen, jute, hemp, as well as silk and rayon may be dyed or printed with Nepthols.
This method of dyeing yields a wide range of shades covering deep yellow, orange, scarlet, red, maroon, violet, brown navy and black the shades are brilliant and in general possess excellent fastness to washing, alkalis, acids and chlorine. Many combinations have very good fastness to light. The shades are also resistant to mercerizing, scrooping and cross dyeing in boiling acid solutions. However, dyeing based on Nepthol AS-G combinations and a few of the blue, violet, black and brown dyeings are also fast to peroxide bleach.
-Textile dyeing and printing
-Tie and dye industries