Sunday, March 1, 2015

What's with this Wool?

Have you ever wondered why sheep don’t shrink when they get wet?  They are ‘wearing’ wool, after all.  And, when we wash the wool we wear, it shrinks, right? 
Technically, wool does not actually shrink, it felts. Wool fibers have a cuticle layer and scales much like human hair, although the scales on human hair are much flatter (remember all those hair conditioner commercials?). When wool is washed, under certain conditions, the raised scales of that cuticle layer catch on to each other, which begins the felting process. 

The fibers in the fleece on a sheep are all growing out of the follicles in the same direction, and at a similar rate.  This means that the cuticle scales are all pointed in the same direction (much like the teeth on a saw blade), and they don’t catch, or lock, on to each other, even if wet.


When fleece is shorn, the processing stages cause the fibers’ natural alignment to get messed up.  As it is cleaned (called scouring) the individual fibers in the fleece no longer line up ‘tip to base’ as they do on the sheep.  They get all jumbled up in various dimensions and directions.  ‘Carding’ realigns the fibers into a parallel arrangement for spinning (roving into yarn/thread) but the fibers are not necessarily ‘tip to base’, so the scales will still catch onto each other.

Drop spinning
When the fibers are spun they come in close contact with each other, and that interlocking nature of the scales helps keep the yarn together.  Felting usually occurs in the presence of heat, water, and agitation which acts as a ratchet to tighten that contact between the fibers in the yarn, and then the yarns in the fabrics.  When the wool fabric gets wet and then dries, the fibers that point in various directions latch on to each other and lock closer together, meaning all the strands of wool pull together tighter than before, and your wool sweater shrinks up! With enough heat, water and agitation the fibers will interlock tight enough to form a solid mat.
The other factor that helps sheep keep their fleece from shrinking is lanolin, an oily-waxy substance they produce naturally. (Lanolin is used in many products designed to beautify, protect and treat human skin.) The lanolin keeps the scaly wool fibers slick and helps prevent them from locking together, and it is removed from the fleece during the cleaning/scouring process.  Shrink-proofing is a chemical treatment that uses chlorine to ‘burn’ off the scales.  It doesn’t entirely remove them, but it does lessen their profile.  The fibers are then coated with a resin to smooth them further.  This allows the wool to be machine washed without shrinking, or felting.

Before and after felting

We use wool yarns (new) that are NOT shrink-proofed to make Snooter-doots.  We want the yarns we use to felt as much as possible to create a solid shell in the shape of the critter we are looking for.  Different brands, styles, and colors of wool yarn felt differently.  We’ll take a look at that next time. We think wool is quite magical, and since it's a sustainable, renewable resource, it's the perfect material to make Snooter-doots with.
Lennie & Bruce inspect our yarn stash.