Spun Silk Yarns.—These yarns are produced in silk manufacture from the cocoons which have been damaged so as to cause the silk to be broken or torn. Such have to be prepared and combed like other short materials and the resultant yarns are in great demand for knitted goods. The perfect cocoons have their fibres unravelled in continuous lengths, a certain number of these being run together to form a single thread of commerce. Artificial silk thread is similar in appearance except that it is not possible to approach the real organzine in fineness of fibre. The spun silk thread is elastic and extremely useful in knitted articles, although its use is restricted to specialities on account of the high price of the product. Illustration 42 gives a photo-micrograph of a common form of spun silk yarn which is two-fold in character, with abundant surface material projecting at all angles. To attain greater lustre and a cleaner yarn, these varieties are often put through the process of gassing, that is, the yarns are passed through a gas flame to have their loose projecting filaments burned off. Fig. 43 gives a view of this same thread where the surface fibre has been singed off and the yarn made much more definite in effect. In the two illustrations the surpassing sheen of the extremely fine filaments is clearly visible; when examined still more closely they give the appearance of lustrous glass rods with very little variation in their structure, absolute plainness being the characteristic.
Fig. 42
2-FOLD SPUN SILK KNITTING YARN
Fig. 43
GASSED SPUN SILK THREAD
Silk and Wool Knitted Articles.—The free use of pure silk yarns is rendered prohibitive in many branches of the trade on account of the enormous price of the yarns, and generally for knitted goods it is not possible to produce a garment of sufficient weight for normal use. If silk is employed for the entire fabric, much of it is lost by intersecting on the back, only a tithe of the material being visible on the face. There is no real advantage in having silk on the back of the texture, and fuller effectiveness and greater comfort and weight are attained by bringing a heavier material on to the back, preferably a woollen thread with the silk showing on the face only. The back woollen thread by its bulk gives greater proportional weight and at the same time pushes the silk yarn prominently on to the surface and enables it to exhibit its full lustre. This is certainly the most effective way of obtaining the utmost utility from the silk material in the texture. The silk and wool hosiery folded yarn is also employed largely for these goods, one yarn of silk being folded in a loose twist with one thread of woollen. In some cases the silk yarn is organzine, in others it is two-fold spun silk, but as a general rule the woollen constituent is composed of wool in the single yarn only, and this loosely spun to give an open effect. This type of silk and wool yarn forms the basis of an important branch of knitted underwear and such garments present an intermediate position between the plain variety of woollen garment and the more costly pure silk article. Fig. 44 gives a view of a typical sample of this class of yarn, being a single thread of organzine silk folded with a single pure woollen yarn. The dense member of the twist is clearly seen to be the silk thread of the organzine variety, because the constituent fibres are continuous and run parallel with each other. Contrasted with this the woollen yarn is free and open in structure, the most suitable type of wool being medium to long staple. In this yarn the lustre and neatness of the silk imparts an elegant appearance to the fabric, whilst the open structure of the woollen thread removes the baldness of the yarn and adds the essential fullness to the handle as well as softness and warmth. In many cases the organzine silk thread is replaced by the ordinary type of two-fold spun silk yarn and the thickness of the woollen neighbour greatly increased over what is here noticeable. In almost every case for such fabrics the silk yarn constituent is pure white and very attractive results accrue if the woollen thread is folded dyed in some bright shade, such as blue, red or green. The lustrous silk yarn with its whiteness tones down the strong colours in a highly pleasing manner and the entire production is of the most elegant description and deservedly a favourite with many classes of wearers.
Fig. 44
SILK AND WOOL KNITTING YARN
Cotton and Wool Mixtures.—Just as we obtain articles of intermediate qualities by adding silk and wool together, so by combining cotton and wool results are obtained which blend the peculiarities of each material. For many wearers pure wool underwear proves rather an irritant to the skin, the crispness making itself felt on a tender cuticle. On the other hand, garments worked entirely from cotton do not possess anything like the power of heat retention as is the case with the pure wool article, and in the important matter of elasticity and absorbency cotton as much inferior to the wool. When the two materials are blended, the resultant is warmer than pure cotton and not so warm as wool, whilst the blended article stands mid-way in absorbency and does not produce the same irritation to the skin as some varieties of pure wool. In regard to whiteness the cotton and wool blend is more satisfactory than many types of wool which have to be bleached in a rather expensive method in order to give similar whiteness. The addition of the cotton improves the colour and obviates bleaching of the garment. Finally, the blended article from cotton and wool is much more moderate in price than the pure woollen garment. For winter its chief drawback is a much lower clothing or heating power, and for the summer its disadvantage is that it quickly fills with moisture and renders the wearer uncomfortable until this moisture has been radiated back again.
Merino.—The great bulk of fabrics of this class are embraced under the term merino, which denotes cotton and wool articles where the materials have been blended in the fibre in a given proportion. The normal yarn is composed of 50 per cent. of each, but the range includes as much as 90 per cent. cotton, with 10 per cent. wool, with 90 per cent. wool and 10 per cent. cotton at the other end of the scale.
Fig. 45
SILK SINGLE AND COTTON AND WOOL MERINO FOLDED 2-PLY