A cotton plant produces boll’s and each cotton boll contains upwards of 250,000 individual fibers. A short staple fiber is up to 1 1/8″ long. A long staple fiber is between 1 1/8″ and 1 1/4″ long. An extra-long staple fiber is between 1 3/8″and 2″ long.
MIC : Micronaire
Micronaire (MIC) is a measure of the air permeability of compressed cotton fibers. It is often used as an indication of fiber fineness and maturity.
For those that have been dealing with man-made synthethic fibers there is a way to relate. To get a ballpark value of denier (fiber diameter) can be calculated by dividing micronaire by 2.82
What Measurement is “Just Right”?
Here’s a breakdown of micronaire readings, from most desirable to least desirable:
Readings of 3.7-4.2: Premium
Readings of 3.5-3.6 or 4.3-4.9: Base
Readings of 3.4-and-under or 5.0-and-higher: Discount
Most of that is cotton grown spun into yarn and micronaire values between 3.7 and 4.2 are optimum for yarn spinning, hence the premium value and the target for farmers. When the measurement comes in too low (too thin), the cotton is more susceptible to entangling around debris, which means too much of the good fiber will also be lost. When it’s too high (too thick), it also causes problems since a coarser fiber negatively affects the spinning process, as well as overall quality. It’s very difficult to spin “high-mike” cotton into fine yarn. As said above, higher micronaire is preferred for cotton purification