qnli question: What is made by placing a plate of blade of copper, brass, or bronze into vat of fermenting wine for several weeks, then scraping off and drying the green powder? sentence: Verdigris is made by placing a plate or blade of copper, brass or bronze, slightly warmed, into a vat of fermenting wine, leaving it there for several weeks, and then scraping off and drying the green powder that forms on the metal.