Wool covers are often used for cloth diapering. Wool is an all natural fiber that has antimicrobial and stay dry properties. Wool fibers naturally contain lanolin which is a waxy substance that repels water and keeps sheep dry in wet conditions. Cloth diapering mamas take advantage of wool's lanolin to keep their babies dry in wet conditions!
Wool is a great natural alternative to synthetic covers like vinyl, PUL, and Fleece. Many people think of wool as being scratchy and uncomforable, and some types definitely can be, but if you find the right wool it is quite comfortable against the skin. In addition, wool tends to feel warm when you are cold and cool when you are warm making it a nice choice in any weather. Most children old enough to voice their opinions say they prefer wool to other types of covers.
Wool covers are used over diapers that are not waterproof. They are typically used with prefolds, flats, or fitted diapers. There are several varieties of wool covers. Wool can be crocheted or knitted into soakers, wool fabric can be sewn together to make pants and shorts, and old wool sweaters can be sewn together to make pants and shorts.
Knitted and crocheted soakers are found in pants form (called "longies") or shorts form (called "shorties"). There are variations on either theme...capris, boxers, underwear styles, etc. The point is that the wool is worked into a shape that will fit over a cloth diaper and prevent the baby from getting moisture all over the house. Both longies and shorties are worn as clothes and do not require pants or shorts over them...in fact, sometimes putting clothes over wool causes the moisture to wick into the cotton fabrics and defeat the purpose of the cover completely.
There are several types of wool fabric that work well for cloth diaper covers. Wool interlock is a knit fabric (stretchy) and it comes in varying percentages of wool. The best for cloth diapering is 100% wool interlock or 97% wool with 3% lycra. The lycra adds a bit more stretch to the fabric and doesn't reduce its waterproofing much at all. Boiled wool is a denser wool fabric that has been "felted" which means the wool has been exposed to hot water and a hot dryer cycle to compress the fibers and make them more waterproof. Any type of wool can be "felted" as I will discuss later. Wool fabric is cut and sewn into shape just like any other fabric would be and is ideal for making "regular" (as opposed to knitted or crocheted) looking clothes to go over cloth diapers.
Wool covers can also be made from sweaters. Such covers are often referred to as "recycled wool". You can rifle through your closet and find that wool sweater that you just never wear, or visit your local thrift store and get some great wool! Look for softer varieties of wool like merino wool, and lambswool, even cashmere! If the wool seems dense without too many holes when you stretch it, then it is ready to cut and sew. If it seems kind of holey, then you can felt it first.
To felt you will put your sweater into a lingerie bag or into a pillow case (to prevent lint build up in your machine) and wash it with hot water and a hot/warm rinse. Then you will dry your sweater (still in the bag) on high heat. This will shrink the wool fibers as much as possible and make them more waterproof. It will also shrink your sweater, so try to get larger sizes if possible!
Once your sweater is felted you are ready to sew! The arms of the sweater can be sewn together to make wool pants and shorts can be made from the body of the sweater. There are many links to websites with instructions for making these. Just google "recycled wool sweaters" or a similar search string.
No matter what type of wool you have, (knitted, crocheted, or sewn) you will want to care for it properly. Wash wool in tepid (not hot and not cold) water by hand and then lanolize your wool. Lanolin can be bought in the stores where you find breastfeeding supplies. Use a pea sized drop of lanolin and rub it in between your fingers to soften it. Then run tepid water over the lanolin as you fill your basin with water. Let your wool sit in the lanolin water for 10-15 minutes and soak the lanolin in. When it is finished, drain the water out of the basin, gently ring your wool out (you can put it in the spin only cycle of your washer too), and let it air dry. Lanolize 1-2x per month (more if the cover is used often) to keep the wool's waterproof properties.
Wool should be washed as needed. It is not necessary to wash it after every diaper change. Hang the wool to dry between changes and wash it approximately once a week. Using this method you should be able to have 5-6 covers.