3.1.2. Syntan after treatment
Table 2 shows the colorimetric data obtained for the 3% omf dyeings which had been after treated with the syntan. Comparison of this data with that of the dyeings which had not been after treated (Table 2) prior to wash testing, reveals that, for each of the three dyes, syntan after treatment reduced the chroma and imparted
a slight reddish hue to the dyeings. These findings were not surprising in view of the shade changes that can be imparted by such an after treatment [1]. The colorimetric data in Table 2 also show that after treatment with the syntan increased the lightness of the dyeings, this being mirrored by a corresponding decrease in colour strength (Fig. 6); these findings can be attributed to dye having been desorbed from the dyed silk during the syntan after treatment process. Fig. 6 shows that the colour strength of the syntanned dyeings decreased with increasing number of washes, owing to dye loss having occurred during each of the five wash tests. However, it is clear that in the cases of the last three wash tests, the extent of the reduction in the colour strength of the syntanned dyeings was lower than that obtained for the corresponding
non-after treated dyeings. Indeed, the fk values of the dyeings which had been subjected to five, consecutive wash tests was higher for the syntanned dyeings than those of their nonafter treated counterparts, for each of the three dyes used, from
which it can be concluded that after treatment with the syntan improved the fastness of the three dyeings to repeated washing. This was confirmed by the lower extent of staining of adjacent multifibre strip materials recorded for the syntanned dyeings after five washes (Table 3). In terms of the reduction in depth of shade that occurred as a result of repeated wash fastness testing, the % colour loss values displayed in Fig. 7 reveal that syntan after treatment reduced the extent of colour loss obtained at the end of the five, repeated wash tests in the cases of C.I. Acid Orange 116 and C.I.
Acid Red 299, but had no effect in the case of C.I. Acid Blue 345.