Many dyers employ iron as post mordant since it shifts the color and also increases the fastness property. Sometimes iron solution is used for the preparation of indigo vat as it is a reducing agent. Most of the natural dyers employ iron solution either made of ferrous sulphate or they prepare it using rusty iron along with vinegar.
Both these iron based formulation has their own disadvantages such as when ferrous sulphate is used for the production of grey or any black shades along with tannin containing plants, the fabric losses its strength after few days since the residual sulphates present on the fabric reduces the strength of natural fibers and finally contribute to fabric deterioration on storage.
On the other hand, preparation of iron acetate takes longer time (around 1 to 2 weeks) and if stored for longer time, the concentration of the solution varies and results in different shades when employed for dyeing. Moreover, the pH of the dyed substance needs to be neutralized properly and thus leads to larger amount of water for post washing treatment using and also alkalis.
Iron is very strong and reacts with natural raw materials that contain tannin and produces
gray, dark grey to black and also should be used with care on protein fibers as it can make them
slightly hard or brittle.
Keeping all of this in mind, with our continuous R&D, we found a new iron based formulation which has neutral pH 7 and do not release residual sulphates or acetates (different from all other researchers & dyers). It's an eco-friendly and sustainable process which was never used before for the production of grey and black shades on all kind of natural fibers.