Wool carpet

It is a protein fibre — treat it like hair

Wool is protein, not plastic, and that single fact governs everything about how it is cleaned. It reacts to alkaline chemistry the same way your hair does.

High-pH cleaners strip its natural lanolin and leave it harsh, brittle and permanently dulled. That is not a stain or a soil problem afterwards; it is a change in the fibre, and it does not clean out.

The three things that damage it

High pH, as above. Standard synthetic carpet chemistry is too alkaline for wool and it comes back changed.

High heat. Wool is not thermoplastic, so it gains nothing from the heat that helps nylon recover, and enough of it causes damage rather than benefit.

Over-wetting. Wool holds enormous quantities of water, and a saturated wool carpet dries slowly enough to invite browning as tannins wick up from the backing.

It also holds a remarkable amount of dry soil

Wool can hold several pounds of dry particulate in a room-sized rug before it looks dirty at all. That is a genuine property of the fibre, and it makes thorough dry soil removal before any moisture the single most important step on wool.

Skip it, introduce water, and the dry soil turns to mud in the pile — which is far harder to remove than the dust it was five minutes earlier.

Which is why identification comes first

Wool is more common in older homes than people expect, both as broadloom and as area rugs, and it is not always obvious by eye. A burn test or a close look at the pile settles it.

On wool the sequence changes: wool-safe pH-controlled chemistry, controlled moisture, careful drying, and on rugs a dye-stability test on every colour before anything gets wet. Older and hand-made rugs with vegetable dyes are where colours run, and a rug that fails that test does not get cleaned in place — it needs a wash plant equipped to handle bleeding.