This verb for an artistic process applying acid to metal comes from the Dutch, & many Dutch masters were good at it
Depending on the process of the application, the surface to which the 
wax is ... and the fatty acids which compose the oil, a process which may be 
modified by ..... Due to the rarity and cost of these pigments, many were 
replicated by using... [DOC] [TLE] A History of Pigment Use in Western Art Part 1 - PCI Magazine [PAR] Jan 1, 2004 ... Good examples of such European Paleolithic art can be found in ... first was to 
mix pigment with animal fat and apply it as a paint with the fingers or a reed.