A yarn count number indicates the linear density (yarn diameter or fineness) to which that particular yarn has been spun. An important consideration in choosing a yarn count is the machine gauge which defines the spacing of the needles in the needle bed (usually as needles per inch).
Obviously, the finer the machine gauge, the finer the required yarn count. Choice of yarn count is also restricted by the type of knitting machine employed and the knitting construction.
The count, in turn, influences the cost, weight, opacity, handle and drapability of the resultant structure. In general, staple spun yarns tend to be comparatively more expensive the finer their count because finer fibres and a more exacting spinning process are necessary in order to prevent the yarn from showing an irregular appearance.
Unfortunately, a number of differently based count numbering systems are still currently in use. Historically, most systems are associated with particular yarn-
spinning systems. Thus, a yarn spun on the worsted system from acrylic fibres may be given a worsted count number.
The worsted count system is of the indirect type based on length per fixed unit mass, i.e. the higher the count number, the finer the yarn. The weight is fixed (1 lb) and the length unit (number of 560-yard hanks) varies. A 1/24's worsted yarn (24 x 560-yard hanks weighing 1 lb) will be twice the cross-sectional area of a 1/48's worsted yarn (48 x 560-yard hanks weighing 1 lb).
The designation 2/24's worsted indicates that the yarn contains two ends of 1/24's so that the resultant count is twice the cross-sectional area (24/2 = 12's).
The denier system is used in continuous filament silk spinning, and when the silk throwsters began to process textured synthetic continuous filament yarns, these nylon and polyester yarns were given denier count numbers.
The denier system is of the direct type based on mass per fixed unit length, i.e. the lower the number, the finer the yarn. The length unit is fixed (9000 metres) and the weight unit (in grams) is variable. A 70 denier yarn (9000 metres weigh 70g) will be twice as fine as a 140 denier yarn (9000 metres weigh 140g). A 2/70 denier yarn will give a resultant count of 140 denier.
The tex system was introduced as a universal system to replace all the existing systems. As tex sometimes produces a count number having a decimal point, it has been found more satisfactory to multiply the count number by 10 to give a deci-tex number. The tex system has not been universally accepted, particularly for spun yarns, and on the continent of Europe the metric system is used for these yarns.
In this book, common commercial practice has been followed, with decitex being used for filament yarn counts and the metric system for spun staple yarn counts. The main count systems, with their continental abbreviations, are as follows:
Bradford Worsted System (NeK) - the number of 560-yard hanks that weigh 1 lb (453.6g).
English Woollen System (NeW) (Yorkshire Skeins) - the number of 256-yard hanks that weigh 1 lb.
English Cotton System (NeB) - the number of 840-yard hanks that weigh 1 lb. Continental Metric System (Nm) (Cotton System) - the number of 1000-metre hanks that weigh 1000g (1kg).
Denier System (Td) - the weight in grams of 9000 metres. Tex System (Tt) - the weight in grams of a 1000 metres. Decitex System (dtex) - the weight in grams of 10000 metres.
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