Wool processing

Reducing (or Drawing)

A top that comes out of a comb will be thousands of fibres thick, while the worsted yarn it will end up as will have around 100 or fewer fibres in cross section. The top has to be drawn out into a thinner roving before it can be spun.

It is essential that the roving must be an even thickness. Tops are reduced through special gills where the difference in the speed between the feed and deliver rollers is greater than in a normal gill box. This pulls the sliver into a much thinner form than gilling.

Special sensors control the speed of the rollers to make sure the roving is absolutely even so it can be reduced down to a fine yarn.

Modern high-draft spinning does much of this reduction during spinning. However, reducing is still necessary to some extent, even with high-draft spinning.

In fact, it was the development of high-draft spinning that led to the semi-worsted system. Before that, manufacturers who wanted yarns that were stronger than woollen yarns had to go to the expense and effort of producing worsted yarns, even though the yarn did not have to be very fine or even. High-draft spinning systems will produce semi-worsted yarns, i.e. coarse yarns made from gill sliver.