On 6 Apr, 21:26, (Andrew Gabriel) wrote:

Funnily enough, the cleaning was done in large vats by Fullers
(I kid you not).

Once Persil was invented, Fullers had to find some other use
for the contents of the vats.

Fullering was treating woolen clothes with Fullers' Earth (an
absorbent, used in cat litter, oil-spill granules and chemical
warfare) to absorb excess lanolin (I think, next stop Wikipedia). It
was also a dry cleaning method.