The aim of dyeing blended yarns and fabrics is to achieve a solid shade in which both fibres are dyed to the same hue and depth. Wool fibres absorb large amounts of dye readily compared to cotton and so the wool component can end up darker than the target shade, whilst the colour yield on the cotton component can be unacceptably low. There are a number of methods of avoiding this problem such as the use of blocking agents to reduce the strike rate on the wool component or the use of neutral or higher pH conditions which also slow down the rate of dyeing on the wool fibre.

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Dye selection is another important aspect of dyeing wool/cotton blends; different dyes are usually chosen for each component, but certain cotton dyes will also dye the wool component allowing a simpler dye recipe to be used. The major dye manufacturers provide information about dye selection for blends and shade matching. Laboratory development work is essential for the particular fibre blend and desired shade.  

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Wool is far more vulnerable to possible chemical damage than the cotton fibre and the extreme alkaline pH and elevated temperatures typically used in cotton processing should be avoided. This is a restriction that applies throughout the preparation and dyeing stages.

 

Michell Wool will work with our development partners in assisting making dye house changes simple and painless.