Munden first suggested the use of a factor to indicate the relative tightness or looseness of plain weft knitted structure, to be used in a similar manner to that of the cover factor in the weaving industry. Originally termed the cover factor but now referred to as the tightness factor (TF), he defined it as the ratio of the area covered by the yarn in one loop to the area occupied by that loop.
The total area covered by yarn is: S x l x d, if l is loop length in mm and d is yarn diameter in mm (assuming the yarn to have a circular cross-section and the fabric to be theoretically flat and not three-dimensional).
Introducing the expression S = ks/l2, the area covering 1 cm2 of fabric is:
A correction for the four areas of each stitch covered by two thicknesses of yarn is then necessary, together with an expression of yarn diameter in terms of linear density.
When comparing structures of the same type and yarn in similar states of relaxation, it is possible to use the simplified formula;
For most plain fabrics knitted from worsted yarn the TF ranges between 1.4 and where N is the worsted count and l the loop length in inches.
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