7.1.6 Yarn numbering and naming

The thickness of yarns, also known as 'yarn number', is expressed in a wide variety of ways. The table below shows how a selection of most common yarn number quantities, indicated on the diagonal, can be converted. The procedure is as follows: 1) On the left vertical axis, select the unit in which the yarn thickness is given; 2) In the top row, select the desired (to be determined) unit; 3) Select the formula for conversion in the box that 'connects' both units; 4) Calculate the yarn number in the desired unit.

Calculation example
The conversion of a yarn with thickness '30 tex' to 'Nm' is as follows:

• The formula is: 'yarn number in Nm' = 1000/'yarn number in tex'

• Yarn thickness of 30 tex corresponds to 1000/30 = Nm 33

The pretreatment is reflected in the yarn's name designation: the term grey or 'ecru' is used if the fibres have not been boiled or bleached; the term 'bleached' is used if the fibres have undergone some form of bleaching.