White tanners used alum (a double salt of potassium and aluminum sulfate) as a tanning agent, for example to make leather (glace) for gloves from goat skin. Finally, the chamois tanners, who are assigned to the white tanning trade, processed deer hides with the tanning agent fish oil into leather for clothing. For all tanners, the raw material water was and is essential for a wide variety of work processes. That is why the Biberach Gerberviertel was located in the depression of the northeastern old town area between the upper and lower Stadtbach. The houses of the tanners reached from the old hospital to the Ehinger Tor. The right to use water for the city streams was regulated by what is known as the stake rate, which in 1976 was still 3.60 DM per year for two stakes (the skins were hung on the stakes for watering in the city stream). At the beginning of the 18th century, 45 master tanners lived and worked here, 22 of them red and 23 white tanners. The former Gerberstrasse was later expanded to what is now the Alte Postplatz by demolishing the church of the Franciscan convent and another house. The Gerbergasse still reminds of this former Biberach craftsmen's quarter.