WW Greener describes the process in much simpler terms. Simply rust, card, repeat til "dark enough", each time rusting in a warmer room, then boil in water with logwood and "soda" (presumably sodium bicarb or perhaps caustic), OR logwood and copper sulphate. Greener also advocates "Burnishing" before if you want the best finish...Oscar says it's a waste of time (of course it is if you then etch the surface).
Oscar's process seems very complicated. He introduces several additional baths (etching bath, and the copperas bath as well...)
I don't like the etch idea at all. I see Parker used sulphuric etch, perhaps Parker damascus requires this due to the specific alloys used. The copperas in Oscar's recipe introduces the sulphate ions, so perhaps this is the equivalent of Greener adding copper sulphate, as there are already plenty of FE ions in the bath from the barrel steel and iron.
Etching probably has two effects. The first is to roughen up the bare metal, maybe it makes the steel portion more likely to rust because it etches more than the iron in the same time. It also raises the iron relative to the steel, protecting the steel from the carding somewhat. I would think that it has the same effect on the rust itself, rust is rust. And it surely makes the whole process longer by removing some of the rust coating.
The reaction (dissolving metal) probably goes a little quicker when the solution is warm, ie in warmer climates.
And I suspect that to get the really nice "copal varnish" finish Greener talks about, you have to polish the metal well, certainly more than 320 grit, and skip the etching altogether.
Anyone care to comment?
