One of the delightful properties of wool is its crimp. With good crimp, a woolen garment has memory, returning to its original shape. Many of us have owned lovely sweaters that, before long, had cuffs that stretched out and didn’t return to hug our wrists – and this is an indicator of poor crimp in the woolen fibers used. Good crimp adds elasticity and spring to the yarn made from crimpy wool.
But what is crimp? How is it formed? Crimp is a waviness found along the wool fibers. The frequency of the crimp, or the number of waves per inch, is somewhat hereditary as is the type of crimp. Those waves can be organized or disorganized. The difference is essentially a superficial one: organized crimp is obvious as all of the crimp in each fiber lines up with the crimp of neighboring fibers making for obvious crimp lines across a section (or staple) of wool – as in the photo on the left. Disorganized crimp has no obvious waves until you look at each individual fiber – the overall look within the staple is more frizzy. When you look at each strand of wool, however, then you can see that each fiber is crimped; they just don’t line up nicely in disorganized crimp like they do with organized crimp.
Crimp can also sometimes be a gross indicator of the type of fiber, since finer wool tends to have higher frequency crimp (more waves per inch of wool) and coarser longwools tend to have less crimps per inch (see a direct comparison of two ewes of our flock who both have lovely crimp for their specific breed in the photo on the right). Although this can give you some insight into the type of wool involved, it is not a good way of comparing two individual fleeces. Although Romneys, as a longwool breed, have less crimps per inch than our Romeldales, a finewool breed, I’ve had some Romeldale ewes whose average fiber diameter fell well into the Romney range – they were actually coarser than many of our Romney ewes – but their crimp looked very much like the finer higher-frequency Romeldale crimp one would expect of their breed. The bottom line is that if you base your assessment of fineness on crimp, you will come across some very disappointing fleeces!
I think the most interesting thing I have learned about crimp over the years is that you don’t always find it in a lamb’s fleece – at least at first. Some lambs are born with lovely crimp all the way to the outer tip of their birth coat, but many who will eventually develop beautiful crimp as they age, begin with a birth coat that is essentially uncrimped. Although this usually resolves itself within a few weeks of birth (with crimp appearing at the base of the fleece as it grows out), I have seen lambs who have been six months old and still have not developed crimp in their wool – and then suddenly it appears. Our little mini-lamb, Odessa, had no crimp for months – even though her brother, Oleg, has lovely crimp. I would constantly check her fleece whenever I handled her, since she comes from Hattie’s line from whom I expect lovely, crimpy fiber. Each time I would check, I couldn’t find a hint of crimp – just straight, soft wool with only a hint of a bend from base to tip. Then, this past weekend, I changed her coat at nearly three months of age and bingo! There was the crimp at the base of the wool next to the skin! It amazes me how this works! Just because a young lamb doesn’t have crimp doesn’t mean they won’t develop it in the next months!