(1)
(2) (3)
Reducing the amount of dye (Mod1) - black from 11% to 8.8%;
- blue from 7.5% to 5%;
- red from 7% to 6%.
Reducing the concentration of soda ash (Mod2) - for the three samples from 75 to 70 kg.
Using citric acid instead of acetic acid (Mod3), as the for- mer being cheaper and less volatile such that it does not leave the garments as alkaline as the latter.
Additionally, an integrated modification combining those above was also implemented.