Also feretto. [a. It. ferretto (di Spagna), dim. of ferro iron:—L. ferrum.] Copper calcined with brimstone or white vitriol, used to color glass.
1662. Merrett, trans. Neri’s Art of Glass, 29. To make Ferretto is nothing but a simple Calcination of Copper.
1753. Chambers, Cycl. Supp., Feretto, a substance which serves to colour glass.
1799. G. Smith, Laboratory, I. 123. Feretto of Spain, is thus prepared.
