Jacquard Loom
Dyeing
Mordant Dyes
There is no standard dye used for silk, some manufacturers preferring one type and others, another. It may be said, however, that as a general rule silk is dyed by the direct method, without the use of an intermediate or mordant agent as in the case of cotton. This is made possible through the natural absorptive powers of silk fibre. Mordant dyes are sometimes used, it is true, salts of tin or iron being employed as the agent; but this method is useful principally when it is desired to weight the silk and restore what was lost in boiling off. As this loss generally amounts to about 20 or 25 per cent and as raw silk is sold by weight, it is easy to see that this, unless recovered in some way, would reduce the manufacturer’s profit considerably.
Winding Thrown Silk into Skeins for Dyeing
Weighting Silk
The process of weighting silk has been greatly abused, as it is comparatively simple to adulterate it, without discovery, to such an extent that the properties of the fibre are seriously impaired. Weighted silk never has the strength or wearing quality of the unadulterated product. However, a certain amount of weighting—to restore a part of the degumming loss—is generally recognized as legitimate, although the percentage permissible is often a matter for discussion.
Both skein and piece silk are dyed by being immersed in vats containing the hot dye solution. The silk is run over rollers which insure even coloration throughout. After dyeing it is dried, stretched on a tenter frame and then submitted to dry heat which sets the dye and adds luster to the silk.
Printing