1032.16
4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800
Wavelength cm
-1
Figure 3.14 FTIR spectra of cotton fabric dyed in combination with iron as mordant
Optimal processing sequence
Mordant concentration of 60 g/l, suggested by Patel et al. [94], was used in this investigation. The reflectance results (K/S values) at a typical incident wavelength of 440 nm for all dyeing–mordanting combinations are shown in Table 3.5. It can be seen that post-mordanting and the PSD (dye) PSD (mordant) sequence for iron (II) sulfate gave the highest K/S value of 2.77 for both dyes. In the case of copper (II) sulfate, however, similar conclusions cannot be drawn based on the K/S values. Pre-mordanting apparently gives the highest K/S of 2.97 for Thar whereas it was post-mordanting with a K/S of 2.48 for Caspian. Considering the fact that both grey and beige are neutral colours, additional factors have to be considered while selecting the optimum process sequence. These factors are 1) the overall shape of the reflectance curve; and 2) the visual evenness of shade under various standard illuminants. Post-mordanting and the PDS (dye) PSD (mordant) sequence yielded a visually level shade and the smoothest curve for copper (II) sulfate as compared to the other sequences. Levelness of shade was confirmed by a less than 2% variation in the sum of K/S values measured across 10 places on the sample.
