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Fibre trash testing

Fibre trash

Trash is not a part of fibre properties but it is important in terms of testing. 

Testing at a different level should give an idea regarding production and in this way trash has a vital part in fibre materials specifically in natural fibres.

The trash has higher importance in terms of commercial accepts of materials as well as procedure fibres in spinning.

According to trash percentage and types of trace, spinning line variable. It also affects yarn quality and the cost of production.

Blow room, carding, and combing machines are mostly adjusted according to lab trash data.

Measurement of trash

Shirley Trash Analyser is used to measure the trash percentage of fibres with the help of the opening and cleaning principle.

It is a box-like instrument with one open end for material feed, one end open for lint collection, and a trash separator box.

This instrument has a feeding roller, two different opening rollers, an Exhausted fan, a Trash box/tray, and a lint collection section.

Shirley Trash Analyser
Shirley Trash Analyser 

To measure the trash of cotton fibres, approximately 100 grams of the cotton sample was prepared. Hard lumps of trash and cotton lint from bales are also weighted with this weight.

To measure trash percentage, feed the cotton sample into the feeding section.

It is necessary to open it by hand and fed it uniformly in a fairly thin fleece. 

For example, when feeding 100g. of the sample, half of it should be spread evenly on the feed table and as the test proceeds, the remaining sample should be added gradually. these are likely to damage the feed plate and licker-in wire points. 

A lever is provided for opening and closing the valve controlling the airflow from the cage into the filter. 

This valve should be opened at the beginning of a test. At the end of each test, the valve is closed so that all the lint falls down into the lint box. 

In this instrument, cotton materials are added into the machine by feed roller, then passes through two opening rollers, with the help of the grid bars and dust extracted system at the second roller, trash is separated from cotton.

Once the trash is separated it falls down and lint is moving further towards the lint collection box.

Shirley Trash Analyser diagram
Shirley Trash Analyser diagram

Here, trash is used as a broad term cause it includes actual trash, dust, and small particles.

To achieve the appropriate result of this test, it is advisable that repeat this test more than one time.

To calculate trash at various levels, give a name to various materials and calculate accordingly.

  • I.e. - S for 100 gm sample, L1 for the lint which comes first, L2 for the second lint, L3 for the third lint, T1 for trash which comes first, T2 for the second trash, L for total lint, and T for total trash.
  • First Check the weight of sample S and then feed it into the trash separator.
  • Once S is processed, Lint L1 and Trash T1 come. Weight this lint and trash individually.
  • Total weight S = Lint L1 weight + Trash T1 weight.
  • Collect trash T1 and feed into the trash separator again, once T1 is processed, Lint L2 and Trash T2 come. Weight this lint and trash individually.
  • Trash T1 weight = Lint L2 weight + Trash T2 weight.
  • Then collect lint L1 and L2 and weigh them together.
  • Therefore total lint weight L = Lint L1 weight + Lint L2 weight.
  • Divide lint weight by the total weight given a percentage of lint.
  • Lint percentage L% = Total lint weight L / Total weight S.
  • Trash percentage T% = 100 - L%.
  • Here, we ignored minor losses. This happens due to some fibres stuck into the instrument or minor weight variation.
  • If we want to figure out this loss then weigh trash T2 and Total lint L.
  • Variation of the sum of the above two-weight from sample weight is loss.
  • Invisible loss = 100 - (Trash T2 weight + Lint L weight).
  • In some cases, Trash T2 also contains a sizeable amount of lint, in this case, one extra cycle of testing is added.
  • I.e. - Collect trash T2 and feed into the trash separator again, once T2 is processed, Lint L3 and Trash T3 come. Weight this lint and trash individually.
  • Trash T2 weight = Lint L3 weight + Trash T3 weight.
  • Then collect lint L1, L2, and L3 and weigh them together.
  • Therefore total lint weight L = Lint L1 weight + Lint L2 weight + Lint L3 weight.
  • In this case, lint and trash percentage are the same as above but the value of L is the sum of 3 different lint and the final trash is T3.

Questions -

  1. Why fibre trash testing is done?
  2. How fibre trash is measured?
  3. What is Shirley trash analyser?
  4. How Shirley trash analyser works?
  5. Draw a flow chart of Shirley trash analyser.
  6. Explain how to calculate the trash at various levels with an example.


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Textile School. (2010, October 27). Fibre Identification - tests to identify a fibre. Textile School

Trivedi, Y. (2020, April 10). Identification of Textile Fibers. Textilesphere.com

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