Hoeing tables and cleaning tanks were used to purify mercury as the final step in the process of converting cinnabar to mercury. Mercury collected in the condensers of a furnace or retort was contaminated with soot, water, dust, sublimed sulphur [sic] and other oxide metals, all of which was called "soot" or "mud." To separate these impurities from the mercury, mud was spread on the hoeing table and mixed with quicklime (calcium oxide - CaO). The lime absorbed the water and captured other impurities, allowing the mercury to flow freely.
The two examples above left are "manual" hoeing tables whereupon a worker used a hoe to thoroughly mix mud with lime and allow mercury globules to coalesce and flow out of a spigot into a catching bucket. The cleaning tank, below left, was powered by an electric motor. The motor turned four rubber paddles to mix the mud with water and lime and allow clean mercury to settle to the bottom of the tank, where it was drawn off through a spigot. This type of cleaning tank was able to operate nearly continuously, freeing the worker to perform other duties.
These three tables were used in the Guadalupe mine from the 1940s until the mine closed in the 1970s. The Guadalupe Rubbish Company donated the tables to NAQCPA in 1987.