As a kid, I remember having terrible experiences with heavy winter gloves. My brothers and I spent a lot of time playing outdoors, building snow forts, sledding and having snowball fights. Most of our gloves and mittens were made of nylon or other fabrics, coated with something waterproof and lined with insulation (polyester or Thinsulate). No matter what they were made of, an hour or two of slush packing, shoveling, digging, etc, would render these gloves worthless - soaking wet and ice-cold. An added bonus of the semi-waterproof coating was the inability to dry these gloves once they were sodden. Running them through the laundry dryer only truly dried the outside, while the inner layers stayed damp and mildewed. Standing them on a floor vent or near the furnace also resulted in a warm, semi-dry state like to an incubator - with the same basic results in terms of internal bacterial funk.
Several years later, I was on an early spring fishing (i.e. beer swilling) trip with some friends on the Pere Marquette River near Baldwin, Michigan. I had yet to appreciate the luck required to connect with a steelhead so I spent much of my fishing time flogging the water with a old fly rig. The March weather was very cold, and my stripping (line) hand was staying wet most of the time. I ended up buying a pair of ragg wool gloves (with half fingers) at one of the local fishing stores. I don't recall why I chose these over the more expensive insulated ones, except that the plain wool gloves were only $10 and I was running low on beer money.
I pulled them on before our afternoon fishing exercise began. Per usual I spent the first hour picking up line, stripping, casting and breaking off flies on the bottom, in addition to unhooking one unlucky white sucker who was perpendicular to my drift and got snagged in the tail. I noticed that, though my gloves were soaking wet, the incessant upriver breeze, falling snow and dropping temperatures weren't chilling my hands into raw, red claws like earlier in the day. I didn't fully appreciate it at the time, but the natural qualities of the wool kept my hands warm while dripping water in the frigid winter temperatures.
There are dozens of waterproof, breathable and insulating fabrics used today in winter clothing. Regardless of the origin or formulation of these, few if any measure up to the basic qualities that make wool an almost-perfect outdoor fabric.
Durability: Wool fibers are very durable and flexible. These fibers can withstand being bent or flexed 20,000 times without breaking. By comparison, cotton will break after 3,000 bends, silk after 2,000 bends, and rayon after 75-100 bends. This tendency to stretch under pressure rather than break also allows the wool fibers to spring back when the tension is released, so wool garments tend to retain their shape. Such natural elasticity makes woolen fabrics resistant to tearing.
Absorbency: Wool can easily absorb up to 30% of its weight in moisture without feeling damp or wet. Unlike cotton (also known as the death fabric), which can hold up to 90% of its weight in water, enough to cause hypothermia, wet wool keeps the wearer warm, if not totally dry and comfortable. Wool functions as a "temperature regulator" and it can protect the body in both cold and warm conditions. Not only is wool so absorbent, but wringing water out of a wool sweater is effective if it gets soaked. In extreme weather or conditions, wool can be a life-saver.
Comfort: As a natural fiber, wool is an excellent insulator. It keeps heat close to the body by trapping still or dead air within the fibers. Wool is also considered to be water repellent. Small amounts of rain or snow will stay on the surface of the fabric until brushed off. Wool keeps you warm even when wet since it retains 80% of its insulating value when saturated.
Wearability: Wool garments do not soil easily, although blood and other proteins may stain them. Wool is also resistant to wear and tear. Another word on wearability - some people have a sensitivity to wool. Their skin can be irritated by wool fibers with a diameter greater than 30 microns. Fibers this thick have been shown to have structural rigidity that pokes instead of bending when brought into contact with skin. With that in mind, try wearing your woollens prior to taking them on a trip. If you find your skin to be overly sensitive, try layering with something between your skin and the wool item. Avoid layering with cotton - a wet cotton shirt will reduce the insulation of your wool sweater.
Flammability: Wool is popular with interior designers because it is considered naturally flame retardant. This characteristic is very useful for outdoor clothing, where campfires, lanterns and camp stoves increase the chances of exposure to fire. Wool won't melt onto the skin like many synthetic fabrics. When exposed to direct flame, it chars or smolders, and will self-extinguish (burning stops when flame is removed).
Natural & Renewable Resource: Sheep are usually sheared in the early spring, so as to be comfortable during the summer. When sheep have an inch of fleece during hot weather, they do best as the wool helps insulate them from the heat. Less than an inch and the sheep can sunburn and overheat. In full fleece, they will definitely overheat. Shearing done by a professional is not traumatic to the sheep, and it's a great way to use a valuable and renewable resource, while helping sheep stay healthy and in good condition.
Finally - Wool garments are not cheap. Consequently, wool is considered a luxury fiber. The high cost of wool clothing has lead to a number of synthetic substitutions, but none offer all the useful properties of wool. Another cost-saving feature used by some manufacturers is recycled wool fabric. I have a jacket and bib overalls made by Columbia (Gallatin Range) from recycled wool. These are cold-weather hunting clothes that I've owned for ten years. I'm not 100% sure how the fiber is recycled, but I've worn them in rain, sleet and snow, bitter cold and driving winds when deer hunting throughout Michigan. I have no complaints about these garments, having lived in them for four or five days at a time - even the price was more than reasonable, as I got both pieces from clearance racks at a major sports retailer. Recycled or virgin makes no difference to me if the overall performance and durability remains the same.
Thanks to the American Sheep Industry Association for some of the wool statistics and information used here.