In the first printed book on metallurgy, the Pirotechnia, Vannoccio Biringuccio describes a process for purifying iron used "outside Christendom": They say that the file it, knead it with a certain meal, make little cakes of it, and feed these to geese. They collect the dung of these geese when they wish, shrink it with… Continue reading Goose poop in the smithy