Wool is an amazing fiber. It is absorbent, insulating, and breathable. These characteristics make it an excellent choice for a diaper cover over prefolds, fitteds, contours, or even other covered diapers as an emergency back-up.
Microscopically, wool fibers consist of overlapping scales (cuticles) that make liquid repel. They are covered with a thin layer of natural oil called lanolin that further causes droplets to slide off. The difference between wool's water repulsion and many other materials that repel water is the air flow. Air still moves through wool and keeps skin feeling dry and temperature-regulated. Wool fibers, beneath the water-repellent outer layer, contain a highly porous and absorbent core. Thus wool can both repel and absorb water simultaneously.
It is worth noting that wool covers will 'compression wick' -- if the cover is saturated and baby sits/lies on it you may feel dampness. The thickness of the wool and the absorbency of the diaper, along with changing frequently will all help to avoid compression wicking. Wool cannot contain a true leak (such as over underwear) if there is too much volume. Wool is only as effective as the diaper underneath it -- but the combination of waterproofness, absorbency, and breathability make it an excellent choice for a cloth diaper cover. I find using wool overnight to be the best possible solution for keeping my boys dry and keeping their skin cool to avoid diaper rash.
Washing wool is different than washing the rest of your cloth diapers. Wool covers need to be handwashed in a wool wash containing lanolin. They should not be put through a dryer as they will felt and possibly shrink or lose stretch. The bonus of wool, however, is that it is antimicrobial and can go for up to two weeks of use (as long as no poo gets on it) between washing.
Nicki's Diapers carries several excellent wool diaper covers and wool washes. I personally love the Aristocrats soakers, and find mine to be absolutely bulletproof for nighttime use over a hemp or bamboo fitted.
By Casey
