SHELL GOLD: How Renaissance painters turned scraps of gold leaf into paint

Gold leaf is extravagant, but gilding produces scraps. The leaf is so thin that it tears, folds, and extends beyond the area being covered. When the excess was brushed away, a careful workshop did not necessarily discard it. The loose pieces and trimmings—what gilders call skewings—could be gathered and made into shell gold: real gold that could be applied with a brush. Historical recipes describe using either fresh gold leaf or the remnants left over from gilding.