159 (#215) ############################################ TWISTING sible; In favour of folding. Against folding. (for single) (for two-fold) 1. Yarn strengthened ; Finer material usually re- quired for spinning single yarn ; 2. Yarn softer spun; More time for spinning and twisting required ; 3. Several colour effects pos- Bursting of thread in finish- ing possibly limited ; 4. Special twisting and varied Special effects such as ran- natural effects possible. dom-most effective for single threads. The strength of woollen yarns is a dominant factor, a twist angle of 20° to 25° giving the best result. In the case of a single yarn-say 30 skeins--this angle will be attained by about 12 turns per inch. If a 2/60 skeins is to be produced, equalling a 30 skeins, then a material capable of being spun to 64 skeins must be employed, and to spin this with an angle of 25° it will be necessary to put in 16 turns per inch. This markedly increases the time taken in spinning, so that not only is there a loss because for the same length of 64 skeins spun only half the weight of material is treated, but there is an additional loss in production due to the additional twist to be inserted. Then on the top of this there is the twisting of the 64-skeins yarn into two-fold 60 skeins- say on a ring frame-with the most suitable turns per inch (see p. 144). Small wonder, then, that few two-fold woollen yarns are employed in any section of the industry. It may seem strange to suggest that a two-fold yarn may be softer than a single yarn ; but that such often is the case will be realized by studying the principles of twisting demonstrated in Chapter XII. Special colour effects-say black and white, brown and white; diamond three-fold twist in brown and white, etc.; and special material effects-say merino and 159
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