Absorbency of Wool
Wool is the most hydrophilic of fibres, meaning it absorbs water while being hollow. In fact it can absorb as much as a third of it’s weight in water and still feel dry. Conversely, it is also somewhat Oleophobic meaning it doesn’t absorb oil as easily and will release oily residues quite easily during cleaning.
It’s wool’s hydrophilic characteristic that makes it so important to remove as much water as possible after the rug cleaning process utilising either a centrifuge or high power extraction and water claw method . This ensures that the rug will dry quicker therefore reducing the potential for problems such as dye bleed and buckling/shrinkage.
Durability of Wool
When wool absorbs water it is both softened and made weaker. The hotter the water the quicker the wool fibre will break down. Strong alkaline cleaning solutions will also cause wool fibres to degrade, as will excessive mechanical agitation. This is why it is so important for wool rugs to be washed under cold water using non alkaline shampoo. The water also acts as a buffer protecting the wool from the agitation caused by any mechanical brushing equipment used during cleaning.
Excessive agitation, combined with high heat and alkaline chemicals is the cause of wool felting and fibre degradation. When wool is rubbed aggressively the scales on the surface of the fibres interlock irreversibly. This is why rugs must never be cleaned in the same way as synthetic wall to wall carpets (using high pH solutions and hot water extraction).
The Dangers of Chlorine Bleach
Chlorine bleach is particularly damaging to wool. In fact it can dissolve wool completely or at least yellow it. This happens because wool is acidic (low pH) and chlorine bleach has a very high pH and so when they combine a neutralization reaction occurs. There are far safer methods to whiten areas of wool on rugs, such as using hydrogen peroxide.
Wool is a fibre which can be damaged with high heat, excess agitation, alkalines and chlorine bleaches, and prolonged contact with water. These factors need to be considered to ensure that wool rugs are cleaned safely. Cold water immersion cleaning using neutral pH shampoos followed by a good water extraction method is the safest way to adhere to this requirement.