Verdigris was made deliberately, not simply gathered as a natural weathering product, by suspending strips or plates of copper over a pot of vinegar in a sealed container, allowing the acetic acid fumes to slowly corrode the copper's surface into a thick green crust, which was periodically scraped off, dried and ground into pigment, a process practiced across Europe from antiquity and described in detail by writers from Pliny the Elder onward. The resulting pigment gave painters one of their only strong, saturated green colors before modern synthetic pigments, though it had real drawbacks: verdigris tended to darken and discolor over time, especially when mixed with certain other pigments, a problem conservators studying old paintings still contend with today when identifying areas of verdigris that have browned or blackened from their original vivid green.
Beyond painting, verdigris served as a mordant in dyeing, as a component in various metalworking fluxes, and in a handful of medicinal preparations applied externally, always with the understanding, at least among careful practitioners, that copper compounds in any quantity were toxic if taken internally. Its ready formation, requiring nothing more exotic than copper and ordinary vinegar, made it one of the more accessible pigments and reagents in the whole alchemical and artisanal repertoire, needing no rare mineral and no difficult metallurgy.