Neil, I just didn't go into as great a detail as you do, usually I am typing on my phone. It is called by various names but gum bichromate printing is an old practice, I use it when doing pt/pd prints. It's a long tedious.and expensive process but the results are well worth it. The Luminier brothers also used gum bichromate and dyed starches to create the first color prints long before Eastman Kodak. That also creates beautiful prints if you have a chance to try it, if you haven't already.