Naples yellow is a dry rock, and pitted like our common rocks that we put in foundations with chalk and sand to give it body; however, it is friable. It is mined from the area around Mount Vesuvius, near Naples, and contains much sulfur; [1] it is very acrid, which one can only remove by soaking it in water, and changing it every day; after this the salt [2] penetrates through the vessel, and appears completely white on the outside; one must also reduce it to powder before letting it soak, & when one burns it on porphyry, [3] never use an iron knife to gather it up, because iron turns it green and black; but for that one can use a knife made of chestnut wood; this color is very good in oil as well as in water.

Notes

1. Naples yellow, or lead antimoniate, was a synthetic pigment and through a misunderstanding many contemporary authors thought it was found or made near Vesuvius or Naples, and that it contained sulfur. See Nicholas Eastaugh, Pigment Compendium: a Dictionary and Optical Microscopy of Historical Pigments (Amsterdam; Boston; London: Butterworth-Heinemann, 2008).

2. The sulfur.

3. See Porphyre.