Photobleaching – the problem
When wool carpets are exposed to light, particularly sunlight, visible colour changes can sometimes be observed, particularly in pastel shades. This effect, known as photobleaching or red shift, may be observed soon after a carpet is laid, a period when consumers are particularly sensitive to product performance. The effect is particularly noticeable when furniture is moved, revealing a colour difference between the areas of carpet which have been exposed to light and those which have not.
Source of the problem
All wool, including bleached wool, will photobleach to some degree, but the extent of photobleaching is influenced by the following factors:
- The initial colour of the wool. The base colour of undyed wool is creamy yellow. The more yellow the wool, the greater is its propensity to photobleach.
- Yellowing resulting from processing, for example, dyebath yellowing and heat yellowing will rapidly photobleach.
- Depth of dyestuff. Photobleaching is less of a problem with carpets dyed to shades greater than 1/12 standard depth.
- Hue. Green and blue shades tend to highlight photobleaching more than redder shades. Beige is particularly sensitive to photobleaching.
Following extensive research, AgResearch Ltd in conjunction with Clariant Ltd have developed and patented a method of eliminating the effect of photobleaching using Lanalbin® APB liquid, a dyebath additive or Lanalbin® S, an in-scour application.