After shampooing a handmade rug it is vital to rinse and extract. Doing so removes residue, sets any unstable dyes and further cleans the carpets’ pile.
An acidic rinse is used to restore the rug to its natural (slightly acidic) state after washing. This sounds dangerous or harsh but in reality it is perfectly safe and normal. Human skin is actually slightly acidic in nature, much the same as wool, whereas the cleaning chemicals used in the cleaning process are alkali. Leaving a rug alkali after cleaning can break down both the colours of the rug and the wool fibres that are used to make it.
One of the issues with non-professionals or those not used to dealing with wool and other delicate fabrics is that once washed the PH balance is not restored, potentially causing colour run, if not in drying then in future washes. This is why some people will have a rug washed, the colours will be fine so when they do it again the expect the same results (as normally any loose dyes would bleed on the first wash) if not better only to find their colours bleed into each other.
The shampoo from the wash is rinsed out with water and a small quantity of rinse agent, this is applied to the rug using a high pressure sprayer which injects the water and rinse into the rug, removing residue and stabilising colours before being extracted by a high powered wet-vacuum. This allows the rug to be dried quicker, meaning the rug is in a damp condition for less time and can dry more naturally.