How to measure a fiber's fineness.

What is micron count? And why should knitters care?

3/6/13

There are a lot of ways to describe a fiber. Most of us fall back on the standard tropes of touch: A yarn is "squishy" or "silky" or "shiny" or "harsh." But these don't actually tell us very much, when you get right down to it.

The best way to describe and study a fiber is by checking its micron count. With the advent of electron scanning microscopy, micron count became a popular and accurate unit of measurement for fiber. Microns are a very small unit of measure: Each micron is one thousandth of a millimeter long. Microns are usually used to measure teeny tiny things like units of infrared wavelength or the size of blood cells.

But microns are also a standard unit of measurement for fibers. Not just wool, although you typically hear "micron count" applied to wool fibers. The micron count when applied to fibers measures the diameter of the fiber. (The length of the fiber is called "staple length," and doesn't affect the feel of the fiber, just the way it behaves when being spun.)

The higher the micron count, the coarser (therefore less soft to the hand) the fiber. You might think that everyone would always want to use a low-micron-count fiber, and in part, you would be right. After all, fine fibers like merino and cashmere are very much in demand. But what those fibers gain in delicacy and softness, they lose in durability. The thinner a fiber, the easier it is to wear through.

This is why the harshest, scratchiest, high-micron-iest wool fibers are typically used to make rugs and carpets. You want it to wear well.

Low micron-count fibers include: