12It will be proper to explain in what manner white lead is made, and also verdigrease, which we call æruca. The Rhodians place, in the bottoms of large vessels, a layer of twigs, over which they pour vinegar, and on the twigs they lay masses of lead. The vessels are covered, to prevent evaporation; and when, after a certain time, they are opened, the masses are found changed into white lead. In the same way they make verdigrease, which is called æruca, by means of plates of copper.
2The white lead is roasted in a furnace, and, by the action of the fire, becomes red lead. This invention was the result of observation in the case of an accidental fire; and, by the process, a much better material is obtained than that which is procured from mines.