Bright white and pastel shade wool and wool-blend products that don't yellow would allow Australian Merino wool to establish a presence and compete with cotton and synthetics.

Vibrant colours for wool clothing

Wool garments in bright, fashionable shades that hold their intensity over time are now a step closer, after studies reveal how sunlight turns wool yellow.

• 10 February 2010 | Updated 14 October 2011

• Background
• Radical turnaround
• Preventing yellowing
• About the scientists

Background

Rapid yellowing of whitened wool in sunlight was first observed and studied in 1956, but a solution to the problem has eluded researchers.

Lack of a solution and doubts about how the yellowing occurs prompted a CSIRO researcher, Dr Keith Millington, to take a new look at the problem.

Wool treated with fluorescent whitening agents soon yellows in sunlight, reducing the intensity of pastel shades applied to it. Whitened wool also turns yellow rapidly in sunlight.

Radical turnaround

In a project funded by Australian Wool Innovation, Dr Millington and Professor Louis Kirschenbaum (University of Rhode Island, USA) discovered that the chemical reactions responsible for photo-yellowing are different from what had previously been reported.

The two researchers found that hydroxyl radicals form when fibres are exposed to light. These highly reactive radicals attack the fibres, leading to yellowing.

For their insights into the yellowing of wool, Dr Millington and Professor Kirschenbaum were presented with Gold Research Medals from the Worshipful Company of Dyers in London in 2003.

In early 2008, Dr Millington was also awarded a Centenary Medal from the Society of Dyers and Colourists in the UK in recognition his  recent review of the scientific literature on the photo-yellowing of wool, published by the Society in their journal ‘Coloration Technology’.

This award caps off 10 years of research into the chemistry and mechanisms of wool yellowing.

Preventing yellowing

Better understanding of how yellowing occurs has led to renewed interest in discovering anti-yellowing treatments for commercial use. This is the goal of a new phase of the project.

If the researchers can devise a commercial process for preventing photoyellowing, Australian Merino wool will be able to compete with cotton and synthetics in the rapidly expanding sports and leisurewear markets, which are especially attractive to the younger generation.

About the scientists

Dr Millington investigates processes that occur when textiles are exposed to light. Some years ago he experimented with the use of UV light to modify the surface properties of fabrics.

This led to invention of the Siroflash process, in which a brief exposure to UV light followed by conventional bleaching is used to prepare wool fabric for printing. Siroflash also improves dye uptake and prevents the pilling of wool and cotton knitwear.

In 1996 Dr Millington won the US Innovative Technology Award from Radtech North America for his work on SiroFlash.

Other members of the research team are:

• Dr Mark Bown synthesised chemicals that may inhibit photo-yellowing when applied to wool during wet processing
• Mr Mike Jones assesses the yellowing tendency of whitened wool treated with anti-yellowing agents
• Dr George Maurdev explores the use of model proteins for studying photo-yellowing, and looking at the role of various forms of oxygen in photo-yellowing.

Find more out about the Project Leader Dr Keith Millington: gold medal winning insights into wool yellowing.