Fulling

Fulling, also known as tucking or walking (spelt waulking in Scotland), is a step in woollen clothmaking which involves the cleansing of cloth (particularly wool) to eliminate oils, dirt, and other impurities, and making it thicker. The worker who does the job is a fuller, tucker, or walker, all of which have become common surnames. The Welsh word for a fulling mill is pandy, which appears in many place-names, for example Tonypandy (fulling-mill ley).

Fulling involves two processes, scouring and milling (thickening). Originally, fulling was carried out by pounding the woollen cloth with the fuller's feet, or hands, or a club. In Scottish Gaelic tradition, this process was accompanied by waulking songs, which women sang to set the pace. From the medieval period, however, fulling was often carried out in a water mill.

These processes are followed by stretching the cloth on great frames known as tenters, to which it is attached by tenterhooks. It is from this process that the phrase being on tenterhooks is derived, as meaning to be held in suspense. The area where the tenters were erected was known as a tenterground.

In Roman times, fulling was conducted by slaves working the cloth while ankle deep in tubs of human urine. Urine was so important to the fulling business that it was taxed. Stale urine, known as wash, was a source of ammonium salts and assisted in cleansing and whitening the cloth.

By the medieval period, fuller's earth had been introduced for use in the process. This is a soft clay-like material occurring naturally as an impure hydrous aluminium silicate. It was used in conjunction with wash. More recently, soap has been used.

...
Wikipedia