Direct Dyes are commonly used on cotton fibers. These
Dyes are mixed in all purpose dyes along with the Acid Dyes. The color
of Direct dyes on cotton fibers is not bright in respect to other dyes.
The wash fastness of these dyes is not very good. The only advantage of
these dyes is that the light fastness is little more better.
Lightfastness means the resistant capacity against fading in light. But,
this is also in few cases only. One more benefit of using Direct Dyes is
that these can be used in the same dye bath with the Acid Dyes.
If anyone wants to get desired result by mixing Direct Dyes with
unmixed cellulose then he/she will have to take these direct dyes in
their pure form unless the use of these dyes become worthless. It is
preferable to use direct dyes on the cellulose fibers. But if these dyes
are accompanied with 'reserving agents' then these can be also used on
stain silk and wool. But, unfortunately the 'reserving agent' is not
available to home dyers.
Few Direct Dyes, like Direct Orange 39 and Direct Blue 86 are
considered as having very high Lightfastness capacity. These two have a
rating of 6 out of 8.
to solve the wash fastness problem for Direct Dyes
In most Direct Dyes, the wash fastness quality is
poor. After every dyeing, these dyes bleed a little with every washing.
This results in losing brightness and also damage other clothes which
are washed in the same load. So, there is a process i.e. 'special after
treatment' can be used to solve this problem. For accomplishing this
process, a cationic bulking agent i.e. RETAYNE is used. This agent glues
the dyes into the fibers. This process is used for dyeing fabric with
Direct Dyes and these dyed fabrics are free from bleeding.
of Direct Dyes
- Few Direct Dyes have low light fastness.
- Many Direct Dyes are bland and dull in color.
- Direct Dyes provide duller color than the color provided by the
fiber reactive dyes.
- The wash fastness quality is also low.
types of Direct Dyes
There are two major types of Direct Dyes:
Cationic Direct Dyes
The main structural features of cationic direct dyes are: (a) the
structural single and double bondings are extended. (b) the molecular
structure is planar, and (c) positive charges are more than the negative
Anionic Direct Dyes
Anionic Direct Dyes are used for coloring papers, controlling tint and
shade and correction of two sided paper color. The main structural
features of the Anionic Direct Dyes are: the planar vary from each
other, the structural single and double bonds are very much extended,
and contains one or more than one sulfonate groups. These sulfonate
groups make them soluble in the water.