56 KANSAS CITY REVIEW OF SCIENCE. 



SCIENTIFIC MISCELLANY. 



TESTS OF SILKS. 



A lady who has visited the most important silk factories in Europe has given 

 the result of her observations in this connection. She says it is next to impossi- 

 ble to detect the genuine article, and that she knows of but four reliable firms who 

 tell the truth about their products. She gives the following suggestions: "If 

 the sum at disposal be moderate, a very good silk is forthcoming, though it may 

 not be a cord ; if a useless dress is wanted, the silk ordered, for instance, is a 

 robe de fatigue, or it is a drap d' Anvers, or a drap de Rhone, the word " drap " at 

 Lyons not signifying cloth, but plain, close textures of black silk. Samples should 

 be written for, and when in hand there is a method for selecting a good silk from 

 a bad one. If, after having made a fold on the cross in a sample received, it is 

 not easily effaced by pulling it over again with the first finger, or by pulling the 

 material in a contrary direction, that silk is bad. If, on the other hand, the ridge 

 imperceptibly disappears, the material is good, for silks should be supple, how- 

 ever thick." 



Another writer on this subject adds some additional hints of a noteworthy 

 character : 



"Formerly, the silk manufacturers used ungummed silk both for warp and 

 weft. The ungumming softens the silk and removes from it a resinous matter ; 

 but there is a great loss of weight — in French silks 25 per cent, but in Chinese 

 silks sometimes 40 per cent. The manufacturers have, for some time past, un- 

 gummed merely the silk for the warp, leaving that for the weft raw, as the threads 

 of the warp are not seen. 



" In this manner a great loss of weight is avoided; but the goods, as soon as 

 wetted, become uneven. This happens especially where such tissues are dyed, 

 when the weft is attracted by the color and the mordant, and becomes rough and 

 broken. Like all other fibers, that of silk consists of a number of small particles 

 linked together. These become prominent on ungumming, so that when a silk 

 fabric consisting entirely of ungummed silk is moistened, no alteration appears. 

 But in common silk goods this only happens with the warp. The moistening, 

 finishing, etc. , of these goods occasion a difference between the threads of the 

 warp and weft. This explains the distortion of such goods, and their tendency 

 to break in the folds," 



Concerning the color of black, there are very unreliable green-blacks and 

 dun-blacks. The real blue-black is the highest esteemed. The raven's-wing has 

 a blue haze over it. It is said that no one not in the business can know how diffi- 

 cult it is to get a glossy blue-black in the matter of silk goods ; a dead black is 



