Cum e candore color mutatus fuerit eritque ater, tollatur lamna ab igni, et sic refrigeratum restituatur in pristinum colorem; sine vitio esse probabit; sin autem permanserit nigro colore, significabit se esse vitiatum.
When the colour is changed by the heat and is black, take the plate from the fire, and let the minium, on cooling, regain its former colour: its purity will be demonstrated. But if it remains black, it shows adulteration.
final_alignments\Vitruvius_Architecture_Book_7.json