From The Canning Handbook, publisheded by W. Canning, plc, Great Hampton Street, Birmingham, 1982, from the chapter on Bronzing and Metal Colouring, page 1024,
ammonia solution, sp.gr. 0.880, 70 ml/l
sodium chloride, 14 g/l
ammonium chloride, 14 g/l
ammonium acetate, 14 g/l
Brush 3 or 4 coats of this solution during the day in intervals of 2 hours, repeat if necessary on the second day. The patina is supposed to develop in a day or two. The handbook says to protect the coating by lacquering or wax polishing. This chapter also covers antique finishes of copper alloys, and is preceded by a chapter on lacquering.
This handbook is unusual in that it is a hardcover text of how to use the proprietary products of W. Canning, which other companies supply in pamphlets, but it is also like an encyclopedia of plating; explaining the science, and showing the art. The book is out of print, there are a few copies around.
I wonder if a new addition will happen, and if a new version would retain the simple style which makes this book seem to come from another era. Actually, the book is from another era, the first edition was printed back in 1901! It really is time for a new addition, since we've learned a lot about new plating solutions since 1982, but the book is still worth having in your library. --tom pullizzi.