ADVANTAGES OF NATURAL DYES: -
1) Health and safety aspects of natural dyes: Though all natural dyes are not 100% safe they are less toxic than their synthetic counterparts. Many of the natural dyes like turmeric, annatto and saffron are permitted as food additives. Many natural dyes have pharmacological effects and possible health benefits.
2) They are obtained from renewable sources.
3) Natural dyes cause no disposal problems, as they are biodegradable.
4) Practically no or mild reactions are involved in their preparation.
5) They are unsophisticated and harmonized with nature.
6) Many natural dyes have the advantage that even though they have poor wash fastness ratings, they do not stain the adjacent fabrics in the washing process because of the non-substantive nature of the dye towards the fabric. An exception to this is turmeric, which shows substantivity for cotton.
7) Natural dyes are cost effective
8) It is possible to obtain a full range of colours using various mordants.
LIMITATIONS OF NATURAL DYES
The limitations of natural dyes that are responsible for their decline are: -
Ø Colour yield
Ø Complexity of textile dyeing process
Ø Reproducibility of shade
Besides these there are other technical drawbacks of natural dyes: -
These are: -
Ø Limited number of suitable dyes
Ø Great difficulty in blending dyes
Ø Inadequate degree of fixation
Ø Inadequate fastness properties except few exceptions
Ø Water pollution by heavy metals and large amounts of organic substances.