Also an unnatural lustre or peculiar bloom may
in parts arise, ruining the appearance of the goods. In some cases the
lime soaps act like mordants, attracting colouring matter unequally, and
producing patchy effects. In the dye-baths in which catechu and tannin
are used, there is a waste of these matters, for insoluble compounds are
formed with the lime, and the catechu and tannin are, to a certain
extent, precipitated and lost. Some colours are best developed in an
acid bath, such as Cochineal Scarlet, but the presence of the
bicarbonate of lime tends to cause neutralisation of the acidity, and so
the dyeing is either retarded or prevented. Such mordants as "red
liquor" and "iron liquor," which are acetates of alumina and iron
respectively, are also wasted, a portion of them being precipitated by
the lime, thus weakening the mordant baths.
_Ferruginous Impurities in Water._--Iron in solution in water is very
objectionable in dyeing operations. When the iron is present as
bicarbonate, it acts on soap solutions like the analogous lime and
magnesia compounds, producing even worse results.
Pages:
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81