What is mercerized?
Any yarn can be mercerized, even wool and I have worked with a lot of mercerized linen in the past but it is most often cotton. The yarn is treated with Sodium Hydroxide (Caustic Soda) to swell the fibres and increase the fibre’s lustre as well as its affinity for dye by increasing the surface area of the fibre. Afterwards, the yarn is soaked in an acidic bath to neutralize the base. By swelling the fibres in this highly alkaline bath, it makes the cotton fibres stronger and “pre-shrunk” because the they don’t retract, so the yarn will shrink less later. The result is a yarn that is smoother and has more lustre.
Mercerized cotton is also gassed (not always but most often). The yarn is passed over a gas flame at an extremely fast speed which singes off any external fibre left outside of the twist. This definitely makes the yarn less absorbent. I definitely prefer non mercerized cottons for towelling and I also feel that it is much more absorbent. I use mercerized cotton for items that are not washed all of the time like runners and pillow cases, 10/2 and 20/2 make beautiful fabrics suitable for summer tops and delicate items. Mills all spin differently. Some put more twist, some less and we get to choose which we like best for different projects. It really does come back to sampling and finding out what you like. One is not right or wrong, they are just different and that is a good thing because it offers us a choice.