The fat is then drawn off the aqueous (gluey) layer, and strained through sieves or filters.
Internally, each purifier is filled with ranges of wooden trays or sieves A, made in the form of purifiers.
The disintegrated ground is then brought back in the trucks and fed through perforated cylinders into the washing pans; the hard blue which has resisted disintegration on the floors, and the lumps which are too big to pass the cylindrical sieves, are crushed before going to the pans.
Some engineers have the sand separated from the stones by screens or sieves and then remixed in definite proportions.
In the wider compartments are placed sieves having sixteen holes to the square inch and bearing zinc turnings.