Summary for waxed patinated bronze surface oxidising Discussion
Waxed patinated bronze surface oxidising is the core problem here: the poster has patinated 3mm phosphor bronze plates for an exterior library entrance using potassium sulphide, ferric oxide powder, weak ferric nitrate, and three coats of microcrystalline wax, but in a very damp workshop the finish is blooming bright green overnight. The bloom wipes off, yet returns quickly, including a white type of bloom, and the poster asks for fast solutions before a deadline. The excerpt also mentions Incralac (a brass lacquer with benzotriazole) as a possible alternative to try. No replies are shown in the source excerpt, so there is no named advice to attribute and no consensus beyond the problem description and the suggested product option.
Q. Hi. I am in Brighton UK. I’ve been patinating 3mm (1/8″) phosphor bronze plates approx. 3′ square to go on an exterior library entrance. I have achieved a mottled red on black background with a solution of Potassium Sulphide, then Ferric (iii) oxide powder applied with very weak solution of Ferric nitrate, finished with approx. 3 layers of microcrystalline wax. Despite the usually reliable wax coating I am quite swiftly getting interspersed blooming, turning bright green overnight in an admittedly vast damp workshop. It wipes off easily but blooming, particularly white type, keeps returning.
The ferric oxide powder should be non-reactive. Can anyone offer solutions I can try? Deadline fast approaching!
Matt Borthwick
Metal Restorer/Finisher/Patinator – East Sussex UK
March 30, 2025