Wool fibres are covered in scales and the fibres tend to crimp or form spirals. The fibres themselves vary in length from 2 to 20 cm and are very fine. Typically only 10-40 microns. Wetting the fibres and adding soap, relaxes the fibres, opens the scales and allows them to move. This along with agitation promotes the entanglement of the fibres and is the basis of the wet felting process.
The photograph shows some Shetland fibres laid out before any water is added. The fibres of this breed are 7-12cm long and are on average 23 microns.
For centuries the only means of dyeing clothing and textiles was to use colours extracted from natural sources. Natural sources include leaves, bark, roots, seeds, lichens and shells. Usually, large quantities of dye material had to be harvested to make a small amount of dye. Economics drove the desire to manufacture synthetic dyes and the first was produced in the 1850s. The use of synthetic dyes grew rapidly and the use of natural dyes and the knowledge about natural dyes declined. Today there is a resurgence of interest in natural dyes.
The photograph shows me extracting colour from madder roots by heating in water.