One of the two forms of dyes, Optimum Quality Direct Dyes are blended in all-purpose dyes, such as Rit. Their colors are duller than fiber reactive dyes, and washfastness is also poor; expect anything colored with them to bleed. The key benefit is that direct dyes can be more lightfast, i.e. resistant to fading in light.
Classification of the Optimum Quality Direct Dyesin Colour Index system mentions to different planar, highly conjugated molecular structures containing one or more group of anionic sulfonate. Due to this reason the molecules are soluble in water. Though, many direct dyes can be received in powder form, it is growingly popular to obtain them as liquid concentrates. The concentrates are easy to manage and meter.
The Direct Dyes are utilized for cellulose fibres such as cotton, linen & rayon. Some dyes in this class are more lightfast than similar colors of fibre reactive dyes. With respect to washfastness, all the direct dyes work rather poorly. Without a proper after-treatment the direct dyes bleed a little with every wash; they lose brightness and damaging other clothing washed in the same load.
There are some specific after-treatments which can be used to figure out this problem. A product called Retayne, acts well to make fabric washable dyed with the direct dyes, without any bleed of the dye. The Retayne is an ionic bulking agent which basically glues the dye into the fibre.
Process of dyeing with direct dyes is very easy. These are a class of dyestuffs applied directly to the substrate in an alkaline or neutral bath. They provide full shades on linen or cotton without mordanting, and can be applied to silk, rayon and wool also.