Yarn Gassing - Quality Checking Method

Singeing quality / effects are checked by the following ways

1. Loss in weight compare to un gassed (gray) yarn,

Weight Loss can be calculated with the help of weighing balance.

                         (Weight of Grey Yarn) - (Weight of Gassed Yarn)

Weight Loss% = ----------------------------------------------------------- X 100

                                          Weight of Grey yarn

2. Available hairs when compare to un gassed (gray) yarn &  Available hair’s length compare to un gassed (gray) yarn

There are two major manufacturers of hairiness testing equipment on the market, and both have their advantages and disadvantages. Some detail is given below.

a)   USTER

USTER is the leading manufacturer of textile testing equipment. The USTER hairiness H is defined as follows:-

H =total length (measured in centimeters) of all the hairs within one centimeter of yarn

(The hairiness value given by the tester at the end of the test is the average of all these values measured, that is, if 400 m have been measured, it is the average of 40,000 individual values). The hairiness H is an average value, giving no indication of the distribution of the length of the hairs.  Let us see an example

	0.1cm	0.2cm	0.3cm	0.4cm	0.5cm	0.6cm	0.7cm	0.8cm	0.9cm	1.0cm	total
yarn 1	100	50	30	10	5	6	0	2	1	0	398
yarn 2	50	10	11	5	10	0	5	10	0	11	398

Both yarns would have the same hairiness index H, even though yarn is more desirable, as it has more short hairs and less long hairs, compared to yarn 2.

This example shows that the hairiness H suppresses information, as all averages do. Two yarns with a similar value H might have vastly different distributions of the length of the individual hairs. 

The equipment allows evaluating the variation of the value H along the length of the yarn.  The "sh value "is given, but the correlation to the CV of hairiness is somehow not obvious. A spectrogram may be obtained.

b)     ZWEIGLE

Zweigle is a somewhat less well-known manufacturer of yarn testing equipment. Unlike USTER, the Zweigle does not give averages. The numbers of hairs of different lengths are counted separately, and these values are displayed on the equipment. In addition, the S3 value is given, which is defined as follows: 

S3 =Sum (number of hairs 3 mm and longer)

 In the above example, the yarns would have different S3 values: 

S3yarn 1 =2. 

S3yarn 2 =4. 

A clear indication that yarn 2 is "more hairy "than yarn 1.  The CV value of hairiness is given a histogram (graphical representation of the distribution of the hairiness) is given.

The USTER H value only gives an average, which is of limited use when analyzing the hairiness of the yarn. The Zweigle testing equipment gives the complete distribution of the different lengths of the hairs. The S3 value distinguishes between long and short hairiness, which is more informative than the H value.

3. Change in Count.

This study may be done by the help of Wrap Reel and Weighing Balance.

4. Change in Color.

This way helps to compare the produced yarn with the master sample of Yarn.