A common test is to put the artificial silk in water, where it will pull apart as though rotten; or to take out one strand of the silk, hold it between the finger and thumb of each hand and wet the middle of the strand with the tongue, when it will pull apart as though rotten.
Artificial silk is inferior in strength and elasticity to pure silk. Then again it is lacking in the crackling feeling noticed in handling the genuine article.
Test for Shoddy. It is no easy matter to detect shoddy in woolen fabrics; the color of the shoddy threads is the best evidence. Many parcels of rags are of one single color, but for the most part they are made of various colored wools; therefore, if on examination of a fabric with a magnifying glass a yarn of any particular color is found to contain a number of individual fibers of glaring colors, the presence of shoddy can be assumed with certainty.
Woolen goods containing cotton are seldom made from natural wool. Shoddy yarns, especially in winter goods, are found in the under-filling at the reverse side of the cloth, as thick, tightly twisted yarns, curlier than those from the pure wool.
Determination of the Dressing. During the various operations of washing, bleaching, etc., the goods lose in weight, and to make up this deficit a moderate amount of dressing or loading is employed. Dressing is not regarded as an adulteration, but as an embellishment.
Various dressing materials are used, such as starch, flour, mineral matters, to give the goods stiffness and feel on one hand, and on the other to conceal defects in the cloth, and to give a solid appearance to goods of open texture. The mineral substances used serve chiefly for filling and weighting, and necessitate the employment of a certain quantity of starch, etc. In order that the latter may not render the cloth too stiff and hard, further additions of some emollient, such as glycerine, oils, etc., are necessary.
When a fabric filled in this manner is placed in water and rubbed between the hands, the dressing is removed, and the quantity employed can be easily determined.
By holding fabrics before the light dressing will be recognized, and such goods, if rubbed between the fingers, will lose their stiffness. Loading is revealed by the production of dust on rubbing, and by the aid of the magnifying glass it can be easily ascertained whether the covering or dressing is merely superficial or penetrates into the substance of the fabric.
The tests of permanence of dyes on fabrics are as follows:
Washing Fastness. Fabrics should stand mechanical friction as well as the action of soap liquor and the temperature of the washing operation. In order to test the fabric for fastness a piece should be placed in a soap solution similar to that used in the ordinary household, and heated to 131 degrees F. The treatment should be repeated several times. If the color fails to run it is fast to washing.