Swedish Occupation: Saltpetersjudare
A Salpetersjudare collected urine soaked earth to assist with the production of saltpeter.
Saltpeter was a key ingredient of black powder (the first gunpowder.) Firearms had been invented around 1400 and required the use of black powder. At the time of Gustav Vasa, the army turned increasingly to the use of firearms. These firearms were charged with powder, which contained 75% saltpeter. Since a high concentration of saltpeter was contained in the earth under the barns, this earth was declared to be royal property. All farmers (the priests made sure that no one was forgotten) had to supply its quota imposed to the nearest salpetersjudare -- it was called the saltpeter tax.
In order to streamline and better control that all the manure soil was obtained during the war years of the "Stormaktstid", special salpetersjudare traveled around among the farming villages. They had the right to even break the stall floor if needed. Moveover, they were to be furnished with food and lodging by the farmer as long as the work was in progress. When they were finished, the farmers had to fill in the new earth themselves and make new floors in the barns. The farmers did not like this forceful practice which was repeated every five years.
After digging up the stable soil, the soil was put in an extraction vat which had a filter layer of sand on the bottom of the vat. The vat was filled with water to separate the soluble components. The Saltpeter solution was then scooped into the reduction pan, a flat copper basin on a hearth. There, the solution was boiled down producing a saltpeter brine. The brine was poured into another vat to crystallize. Copper sticks in this vat collected the crystals. The saltpeter was then scratched off the copper sticks and the rest of the brine went back to the reduction pan again.
From the middle of the 1700s everything that could give saltpeter was taken advantage of and collected, such as waste contents and rotten meat from the households in the cities. The compost was then boiled and leached. Working conditions were very difficult and the staff often consisted of female prisoners under the supervision of the salpetersjudare and guard personnel.
(Note: The correct spelling for saltpeter in modern Swedish is salpeter but in records before the 1900's is often found spelled saltpeter and the occupation as Saltpetersjudare. The correct spelling in English is Saltpeter. Saltpeter can be either potassium nitrate or sodium nitrate.)
Svenska wikipedia, Saltpetersjudare, http://sv.wikipedia.org/wiki/Salpetersjudare
Ulrich Bretscher’s Black Powder page, Saltpeter, http://www.musketeer.ch/blackpowder/saltpeter.html
Wise Geek, clear answers for common questions, What is Salt Peter?, http://www.wisegeek.com/what-is-salt-peter.htm