Have you ever heard of mercerized wool? Perhaps you have. However, wool in fact cannot be mercerized!
You may well have heard of mercerized cotton. The original process is the treatment of cotton thread or cloth with caustic soda (NaOH) while the cotton or thread is held under tension. The method was developed in the 19th century by John Mercer and H.A. Lowe (source: Wikipedia). The properties of the fibre change by swelling. As the next pictures show, there is a difference in the cross section of the fibre before and after mercerization.
Some advantages of mercerized cotton are: more lustre and a better absorption of dyes. It is also said to be stronger, which is why it is often used for better quality T-shirts and jeans. Please see below a photograph of mercerized cotton with a nice lustre:
Can mercerized wool have the same treatment? Definitely not! Wool could not resist this treatment with caustic soda.
Why then is it called mercerized wool? Probably for the simple reason that it has improved qualities in comparison with non-treated wool.
As you may know, wool is rather susceptible to shrinkage due to felting and can sometimes be stiff and prickly. It is generally believed that the finer the wool type the better it feels. It is an issue whether or not every type of wool is washable. This has to do with the scale structure of the fibres (whether it is the fleece of sheep or coat of other animals, such as the angora rabbit, the cashmere goat, the yak etc.) and the way in which the scales can lock down, as you can see below:
There are treatments to make wool more washable, more lustrous and softer against the skin. There is, for example, a chemical treatment (mostly with a chlorine composition) which destroys the scales on its surface so that the wool tangles less easily and the garment is better washable. There is a treatment which applies a thin silicone film over the fibres making them smoother and feeling more comfortable. This also gives the fibres more lustre and makes them less prone to shrinkage. This condition, however, may change after a number of washes.
Both treatments have nothing to do with the original mercerizing. In fact, they may even be considered an unlawful use of the term. The treatment, however, has a positive effect on comfort and washability of the garment…
If you have any remarks or additional information, please let me know.
Chris Koeleman, Q&A Quality Assistance