That is a loaded question! I read early on in my researching cloth diapers that wool was the best night time solution but was somewhat incredulous. It was some time before I earnestly investigated the matter. Even then, I didn't totally believe it until I tried it! It just sounded too good to be true! As it turns out, it is fascinatingly and completely true! Why should I be surprised?
Here are some perhaps overly-simplified, but hopefully still accurate descriptions of what I've learned about wool:
-It can absorb up to a third of its weight in moisture without feeling wet because the outside of wool fibers are water resistant, but the inside of the fibers attract water. Unlike most absorbent materials, the moisture is distributed evenly throughout the whole soaker or cover and not concentrated in one place.
I could barely believe it the first time I left my very heavy wetting baby in a wool soaker all night, only to find in the morning that it barely felt damp, nothing around her was wet, and what more, when I took off the soaker, the diaper underneath was not saturated like usual but merely damp as well. I was simply amazed.
-It keeps baby cool in the summer and warm in the winter. The texture and coil-like shape of the wool fibers makes them stick to each other or mat together, creating a mesh with many pockets of air which allow the fabric to hold heat in, and keep it out. It works similar to the way that insulation in a house works.
When it comes to avoiding/fighting diaper rash, I find it just as effective to put a wool cover over a fitted as putting on just a fitted because it is not only is it breathable, but it actually absorbs moisture from the diaper, pulling it away from baby's skin. It never ceases to amaze me that I'm putting the same thing on my baby when I want her to be the warmest (now that the cold weather is setting in) that I put on her when I want her to be the coolest during the hot summer!
-It resists bacteria AND does not retain odor. The scaly surface of wool fiber does not draw bacteria like other fibers, and impedes microbes and dirt from entering, so it cleans easily because they are not embedded inside of the fibers. I don't understand how all of this works, but I've deducted that the structure of the fiber also allows it to trap chemicals that cause odor.
Not only that, but lanolin, the natural oil found on sheep's wool (that is mostly removed during processing but widely available to consumers and easy to re-apply) has anti-bacterial and anti-fungal properties intended to protect the sheep from infection, as well as also being water resistant which serves to enhance those same properties of the wool fibers themselves.
For this reason you only have to wash your wool every couple of weeks, and lanolize it every month or two, depending on how often you use it! I have been amazed that though my baby's wool soaker does smell slightly of urine after wearing it all night, after hanging on a peg for a little while, I take a sniff to find it has no odor at all.
Wool is also known for being durable, flame resistant, and resistant to static electrically (which also makes it less attractive to bacteria).
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