Everything you didn’t know about wool: wool processing

As we enter into the holiday season of December, the colder weather got me thinking about the warm clothes that we wear.  Often we garb ourselves in holiday finery which may be a special occasion sweater made of wool.   Since some parts of the Waushara, Marquette, and Green Lake counties were historically farmed with sheep and other small livestock, I thought some information about the transformation of fleeces to the end product would be of interest.

The process of taking raw fleece from a sheep to wool fabric is a complex one that many aren’t familiar with.  Wool is generally used for two purposes, apparel (clothing) and carpets.  Apparel wool generally is a smaller diameter fiber than carpet wool.  Wool fiber diameter is measured in microns (µ).  The smaller the micron measurement, the finer the wool fibers.  Coarser fibers tend to be more “scratchy” or “itchy”.

common fabric fiber types viewed under a microscope

Microscope view of some commonly found fibers. Note the more protruding scale of coarse wool compared to the other fiber types. Photo from https://goo.gl/uWZXwP.

Once the fleece is sorted to an end-use, the wool will be processed.  There are two systems of processing fleeces: the worsted system and the woolen system.  The worsted system uses all new, previously unprocessed wool whereas the woolen system uses some new wool and some that has already been processed along with other recycled wool materials.  Generally shorter staple wool fibers are used in woolen processing.  In the worsted process, the wool fibers are aligned in the same direction, making the yarn from this process smooth and compact.  In contrast, woolen processing allows fibers to be randomly placed, making the yarn fluffy.

Scouring is the first step of processing wool, usually done with a detergent.  This step is to remove the lanolin from the wool, what makes a fleece feel “greasy”.  Wool that is contaminated with excessive vegetable material may go through an extra step called carbonizing.  This is using an acid treatment followed by heating which converts the vegetable matter into carbon that can be shaken from the wool.  After scouring and carbonizing, the wool is dried with blowing hot air.

Following drying, the carding process begins.  Rollers covered with short wire bristles separate and untangle the wool fibers.  Blending of different fiber diameters may occur before or after carding.  Once blending and carding have occurred, the wool goes through a combing process.  This further removes any vegetable matter and continues to untangle fibers.  Long wool fibers are being arranged in a parallel manner while short fibers, called noils, are combed out.

Next, roving is drawn out from the now parallel long wool fibers.  What starts out as a sheet of wool fibers is subdivided into smaller bunches of wool fibers which are still bulky.  Once the wool is divided up into roving, the roving is spun into yarn.  Yarn is wound around a cone or tube, then used for weaving of fabric.  The finishing steps are anything done after the fabric leaves the loom, such as dyeing of fabric.

If you are curious and want to see some of the steps, you can view a video on how wool is processed at https://goo.gl/Kc4gVg.

So the next time you throw on some warm wool clothes, think of the complex process that the wool had to go through to make the fabric you are wearing.

The University of Wisconsin-Extension provides research-based information to help citizens of Wisconsin make informed decisions based on science.  UW-Extension extends the boundaries of the university to the boundaries of the state, helping the people of Wisconsin and beyond access university resources and engage in learning, wherever they live or work.


Note: This article originally was published in the Marquette County Tribune, Waushara Argus, and/or the Berlin Journal.  This article was written by Lyssa Seefeldt, UW-Extension Agriculture Agent for Marquette County unless otherwise noted.