2.5.7 Avoiding the Problem

• Arrange for your garments to be tested before they are supplied to retail.

• The phenotest has been shown to be useful in controlling the quality of white and pastel goods.
  
  
• This test is intended only to predict the yellowing which may be caused by the action of oxides of nitrogen on yellowable phenols.

• It is NOT intended to deal with any other causes of yellowing such as fading of optical brighteners, gas fume fading or fading of softeners.

• Further details of the test and testing equipment are available at www.pp-t.co.uk.
  
  

The test is intended only to predict the yellowing which may be caused by the action of oxides or nitrogen on yellowable phenols. The test is not intended to deal with any other causes of yellowing such as fading of optical brighteners, gas fume fading or other such causes.

Phenotest has shown to be very useful in controlling the quality of white and pastel coloured goods and can significantly reduce customer complaints due to this factor.

2.8 Concluding Remarks

Four kinds of yellowing are commonly known:

• Yellowing by oxides of nitrogen. Found on Cotton, Acetate and Nylon. Caused by reaction between dye (reactive and disperse) and nitrogen oxide gas (retained in the fibre by exposure to gas stoves, vehicle exhaust fumes). The problem can sometimes be resolved by Dye Selection.
• BHT in packaging.
• Yellowing of the softener used (on heating). This is an entirely separate subject, with different reasons, causes and mechanisms. It is a processing issue rather than one which arises in the storage and transit of finished goods.
• Fading of optical brightening agents. One example of an OBA to prevent yellowing available from BASF is enclosed here.

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