White Wool Technology Package

Photo: Black Rose Photography

The off-white to creamy-yellow colour of wool is determined by the chemical make-up of the keratin in the fibres and is a critical issue in its suitability as a fabric for particular markets. Spring and summer fashions are dominated by bright or pastel colours. Cotton, acrylic and polyester can be made much whiter than wool and can therefore be dyed to bright pastel colours required for these fashions.

The colour of wool is also affected by ultraviolet rays in sunlight. When wool is exposed to sunlight the fibre slowly turns more yellow. This is referred to as photo-yellowing. This can happen when the wool is on the sheep and after processing when the wool garment is exposed to the sun.

There are weak relationships between the whiteness of wool and the content of some minerals in wool. Yellower wools tend to have slightly higher manganese and slightly lower zinc, iron and copper content. How the minerals affect colour is not known and the effect of mineral supplementation has not been investigated.

Finer wools appear whiter due to the way light reflects off finer fibres.
The colour of wool is moderately heritable (part of which is explained by fibre diameter), allowing its inclusion in a selection program. However, preliminary results for photo-stability, show it to have a low heritability.

Wool also becomes yellow when exposed to heat. For this reason temperatures are kept to a minimum when processing wool.

The Sheep CRC is conducting research on whiteness and photo-stability of wool to determine whether there are practical and effective ways to improve and maintain wool whiteness through breeding and processing.

Potential Benefits:

• Significantly whiter and brighter woollen products with acceptable photostability;
• Wool able to compete with cotton and synthetics in markets, such as next-to-skin transseasonal knitwear.

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