Wool

Most mistakes on wool cannot be undone. The scaly surface of the fibre interlocks wherever alkali and mechanical action rise together; the fabric shrinks, hardens, and never comes back.

Why is felting irreversible?

The surface of a wool fibre is covered in scales that overlap like roof tiles. Wet and agitated, those scales are forced to slide in one direction only: fibres work into one another and never separate again.

Three factors drive it, and all three are controllable in finishing: alkali, temperature and mechanical action. A bleaching condition that is unremarkable for cotton leaves permanent damage on wool within minutes.

The practical consequence: a wool recipe is not built around how much it cleans, but around which limit it stays under.

What limits apply in washing?

Wool is washed near neutral at a moderate temperature. The washing agent's job is to carry enough emulsifying power to lift oil and soil inside that narrow window.

In the catalogue this falls to the speciality washing agents family. Products formulated for wool and wool blends are built to do the work with low mechanical action.

Mechanical action is part of the recipe too: raise the liquor ratio, reduce machine speed, ease rope tension. Chemistry does not compensate for getting these wrong.

How is a common window found in blends?

Wool usually arrives blended with polyester or polyamide rather than alone, and then the two sets of conditions collide:

• Polyester wants harsher pre-treatment than wool will survive.
• The neutral, warm conditions that are safe for wool are weak at removing the spin finish carried by the synthetic.

The recipe is built in the narrow band where the two limits overlap, and products are chosen accordingly. The blends page goes into this trade-off.

Dyeing and finishing

Wool is dyed with acid dyes under acidic conditions. Levelness is controlled with levelling agents; the temperature rise is kept slow, because fast heating produces both unlevelness and fibre damage.

In finishing the target is a soft, full handle. Softeners are used for this, with stenter temperature held below the point where wool yellows.

Which product groups are used on wool?

Washing agents, wetting agents, dispersing and levelling agents, anti-creasing agents, antifoaming agents and finishing agents.