"Dogs'-dung is called 'pure', from its cleansing and purifying properties"
When Henry Mayhew published his massive work London labour and the London poor (1851), one of the occupations he described was that of a 'pure-finder'. This was a person who collected dog faeces for sale to tanneries.
Mayhew gives us a short history of the term, noting that it was fairly new in coinage. He published his work in 1851, but only 20 or 30 years before this, pure-finding was not an established profession, instead being one of many sources of income for 'bunters', rag ladies who picked through garbage piles for anything of value. At that time it was a job for elderly ladies who were not fit for more strenuous work. But the market for dog droppings grew as London grew, and by 1851 pure gathering was often the primary profession of able-bodied men and women.
The customers for 'pure' were the tanneries in the Bermondsey district of London, which would buy all that could be brought to them -- they used it as a siccative for fine leather such as that used in bookbinding and kidskin. There were approximately 30 tanneries in this district, and an estimated 200-300 pure-finders delivering to them. Unfortunately, the number of new pure-finders entering the market kept it from being an up-and-coming sort of profession.
Pure finders were paid by the pail, from 8 pence to as much as 1s. 2d., depending on quality. Mayhew notes that the pure-finders included a higher class of scavengers, as a respectable collector with some decent social connections is more likely to find permission to clean out kennels. There was also a lower class of pure-finder, those who scavenge directly off of the street. Those cleaning kennels, he reports, might earn as much as 10 to 15 shillings per week -- around about $100 dollars in today's currency. The street collectors might earn half as much. A true underclass of pure-finder was emerging at this time, however, as the children of the "starving and destitute Irish" would also collect pure, but not knowing where to take it, would sell it to the established pure-finders for 2-3 pence a bucket.
"The pure-finders always carry a handle basket, generally with a cover, to hide the contents, and have their right hand covered with a black leather glove; many of them, however, dispense with the glove, as they say it is much easier to wash their hands than to keep the glove fit for use. The women generally have a large pocket for the reception of such rags as they may chance to fall in with, but they pick up those only of the very best quality, and will not go out of their way to search even for them. Thus equipped, they may be seen pursuing their avocation in almost every street in and about London."
In 1843 Charles Cochrane had instituted new profession -- that of the street orderly. These were members of the lower classes that were paid to clean the streets -- much to the distress of the pure-finders. In addition, new tanning methods were soon to appear, most notably chrome-tanned leather, which would be invented in 1858, that would lead to the decline and fall of the pure-finders.
London labour and the London poor: a cyclopaedia of the condition and earnings of those that will work, those that cannot work and those that will not work, Volume 2, Henry Mayhew
Cass, 1851.