Cover of the Cloth and Reed Marks
Reed marks are caused in the fabrics due to damaged reed,bent reed wires,wrong denting etc.If a coarse reed is used in weaving a fine sort,reed marks will also be apparent all over the fabric.
The position of the warp line in a loom has an important effect on the production of the cloth,since the height of top and bottom lines from central line of the shed governs the relative strains put up on the warp ends.If the warp threads move equal distance at the top and at the bottom lines from the center,the strain on both the lines of the shed will be equal.If this measure is adopted in a plain weave,the warp thread will lie in pairs in the order of denting,causing a reedy hard appearance in the cloth.Cloth showing this appearance is a 'bare cloth'. This is a serious defect in plain cloth.
Cover of the cloth
To remedy reed mark in cloth,the back rest is raised without altering the position of the healds.The top line of the shed will then be smaller and slack,and bottom line of the shed is bigger and strained.This method of alternate slackening and tightening the warp ends in successive picks is termed as 'troughing the shed'.By this it will spread the warp yarns that form the top line of the shed between the warp yarns that form the bottom line of the shed at the time of beating up.The ends will be evenly distributed and the cloth will be soft and smooth.This appearance of the cloth is known as 'cover'It should be remembered that the warp line cannot be raised beyond a certain limit,because the increased strain on the bottom line of the shed cause them to break.Secondly too slack top shed will obstruct the weft yarn insertion in to the shed and cause 'stitching defect' in the cloth.
Troughing the shed is sometimes adopted for twill and sateen weaves to make the effect more prominent.The diagonal ridges of twill weaves become more prominent when the method of Troughing the shed is adopted in looms.
With a plain weave,beating up with a crossed shed and producing a slack top line and tight bottom line to obtain good cover cloth,it become necessary to make the shed early,so that no reed mark will be noticeable.
A tugger cord runs from the front lease rod to the top of the reed cap over the healds and lifts the warp to slacken the top line and to tighten the bottom line of warp threads at the time of beating up for equidistribution.The cover factor is,therefore,an important point for assessment of the quality of plain cloths.
