Thoughts On Why Wool Felts

THOUGHTS ON WHY WOOL MAKES FELT

The following is a fast overview of why wool makes felt. This is all theory gleaned from many sources. It is not actually known exactly why wool makes felt.

SCALES “OPENING”

When fiber is moistened, the inside of the shaft begins to swell, causing the scales to push out away from the shaft. (To appear to “open”.) pH conditions above 8 and below 4, also contribute to this swelling. (Soap is pH 8 and above, depending on its formula while dish detergent is usually pH 7 which is neutral.)
AGITATION/ FIBERS MOVING ROOTWARDLY
When the fibers are pushed (agitated) they begin to move. However, the scales are attached to the shaft at the side which is towards the root. So this means the fibers can only move in a rootwards direction. Most carded fiber or woolen spun yarn have the fibers arranged randomly, so that the roots are facing in all directions. When the fibers are wetted and agitated they begin moving in all directions (but towards their own roots. )
CRIMP
The individual fibers are crimpy. As the fibers move, they begin to corkscrew around each other, becoming entangled.
WOOL ELASTICITY
As the fibers move forward, they are stretched. When the agitation is relaxed, the fibers compress again because of their elasticity. This causes even more entanglement than the crimpiness of the fibers, because the tip end of the fiber springs forward. (Following the root end.)
TEMPERATURE
The scales will open more at a higher temperature. According to my research, cold temperatures do not cause the scales to close. In fact, I have not found evidence that radical changes in temperature cause the felting. But high temperatures do help the scales to open more.
Other Observations:
The scales do not “close”, causing the entanglement. The scales, crimp and elasticity combine to cause the fibers to entangle.
People do cause the scales to close again when they give the felt a vinegar rinse after it is completed. This returns the wool to its normal 4.9 pH.

Return to feltmakers list FAQ