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Simply put, crimp is the natural shape of fiber, created as a result of the growth process. But what does it mean, and how do spinners use it?
Talking About Crimp + Examples
Often used to describe wool, crimp can present itself as wavy or curly, dense or loose, organized or disorganized. The crimp in locks of fiber can be flat or three-dimensional, sometimes even taking on a ringlet shape.
Some spinners also use crimp to determine the fineness of a fiber, with more crimp indicating softer fibers. In this model, less crimp indicates a fiber is more coarse—though that is a very broad generalization and should be taken as a starting point only. Let’s take a closer look at crimp with a few examples.
Merino
Merino is a fine wool with a fine, tight crimp that is about 12 crimps per inch. Yarn spun from Merino is often considered bouncy and squishy.
Merino locks in natural colors from Chaotic Farm in Medina, Ohio. Photo by Matt Graves
Romney
Shepherd Martha Owen counts Romney sheep among her flock, saying:
Romney is bright and luminous and takes dye in a fantastic iridescent way. The crimp is a ripple, not a frizz. The fibers are large. It feels heavy in your hand.
With micron counts ranging from 29–37, Romney is often used for outerwear and rugs, though some of the finer fleeces may be suitable for next-to-the-skin wear.
Martha also looks at how other breeds impact Romney’s crimp. Take a look at the difference between Judy and Petra Parsnip’s fleeces below. Petra Parsnip, a Romney x Bluefaced Leicester cross, already has much more distinctive curls thanks to her Leicester genetics!
Learn more about Martha’s flock in A Shepherd’s Perspective: Romney and Romney Cross.
Woolly ewes in Martha’s flock (from left): Judy, a Romney, and Petra Parsnip (Romney x Bluefaced Leicester). Photo courtesy of Martha Owen
Border Leicester
Some longwool breeds have more standardized crimp styles from flock to flock, but Border Leicesters have a lot of variety in the United States. Within contributing editor Kate Larson's flock, she has sheep with round, curly ringlets; flat, wide waves; and flat, tight waves. All of these are useful and can be spun into a variety of lovely yarns. Kate also says:
As a longwool shepherd, I’ve always loved the term “strong wool.” Most of the time, “strong” means “coarse.” However, “coarse,” or the loathsome “scratchy,” descriptors tend to bring a negative connotation. I find the term “strong” in older resources, which would have found important roles for durable wools. Strength is an attribute.
Find Kate’s tips for spinning these lustrous fibers in Spinning Strong Wools
Kate enjoys having several crimp styles in her flock of Border Leicesters. Flora's fleece shown here grows in flat locks that have a tight wave pattern. Photo by Kate Larson
Some Rule-Breakers
If the exception proves the rule, then there are plenty of exceptions in the “rules” that define crimp. Let’s take a look at just a few.
Double-Coated Fleeces
Adapted from Double Coated Wool by A. Sabine Schröder-Gravendyck.
Double-coated fleeces can actually include up to three types of fiber: a coarse, wavy outercoat, a softer undercoat with different crimp to the outercoat, and kemp, or hair, which is coarse and wiry. This results in several kinds of crimp in the same place! Sabine writes:
These so-called mixed-wool fleeces can ask for a different preparation approach compared to uniform fiber fleeces, such as we might find on a Corriedale or Merino. We can separate all the various fibers, blend the whole fleece together, or a bit of both. I want to help spinners embrace these complex fleeces and see them as opportunities to explore a huge range of handspun. While Skudden fleeces might be difficult for you to locate, breeds such as Icelandic, Spelsau, Hebridean, and more, have mixed fleeces, too. You might find some Shetland with a transition or double-coated fleece.
Locks from different areas of a Skudde sheep fleece. Note the variety of crimp! Photos by A. Sabine Schröder-Gravendyck
Mohair
Adapted from Choosing Fiber: Where to Start by Diane Lalomia
With its lustrous curls, you might be tempted to class mohair with strong longwools at first glance, but that’s not always the case! Kid mohair can be incredibly soft and luxurious! Diane Lalomia writes:
Fiber produced by the Angora goat is not called angora, but rather mohair. Mohair can vary from 14 to 90 microns; the finest mohair is referred to as kid mohair. Typically, kid mohair comes from a younger goat, but an older, well-bred goat may have less than 1 percent of medullated fibers (medullated, or kemp, fibers have a hollow core—see page 56), and its fiber can still be classified as kid. The epidermal scales in mohair are faintly visible, scarcely overlap, and lie close to the stem with a very smooth appearance. These properties allow the smooth surface to reflect light, giving it a beautiful luster, and mohair has much less tendency to felt than wool. Kid mohair blended with fine wool will produce a strong fiber that drapes and dyes beautifully.
Mohair. (from left) Fall kid, first clip, 23–30 microns; Spring kid, second clip, 23–30 microns; Yearling, third clip, 31–35 microns. Photo by Joe Coca
How to Use Crimp in Spinning
With all the different kinds of crimp, what’s a spinner to do? The most common use of crimp is as a stand-in for fineness. While it’s true that a denser crimp can result in a finer animal fiber, and more open crimp structures are often shiny, there are exceptions to each of these “rules!” Few spinners have access to micron testing, but our hands are excellent judges of softness—what feels soft, and what feels strong? Does the fiber feel smooth and silky? Take a look at it, too—is the appearance matte or shiny? All of these things join the mix of crimp, softness, and strength that make animal fibers so unique and interesting.
Beyond simple qualitative observations, some spinners use a method called spinning to the crimp—a technique employed by Anne Field and Mabel Ross—where the distance between each crimp impacts the overall thickness and amount of twist in your yarn. It can be an interesting start to a breed study, but as our exceptions to the rule show, it’s a starting point. If it gets you to a yarn you love, wonderful! If not, keep experimenting.
The final verdict on crimp in wool? It’s just one factor among many that defines the properties of fiber. Observe it, measure it if you’re so inclined, and see where it takes you!
Resources
- Want to use crimp to choose your spinning approach? Read Beth Smith’s article, Spinning with the Crimp in Mind in Spin Off Winter 2011.
- Prefer a more intuitive approach? Read Amy Tyler’s article, Hooke’s Law and Stretching Wool in Spin Off Summer 2025 for a fascinating explanation of why skeins of yarn that are the same length don’t always look like it!