Hello,
Jon N, I too have found the whole Chemical Blackening process a bit variable. There seem to be a number of variables that affect success. The first is the type of metal, nickel silver and some steels seem particularly awkward. Then there is the surface finish , polished, cast or hard surfaces don't blacken as well. The part to be blackened has to be very clean and grease free. Some sort of mild acid cleaning solution works well. It is as well to dilute the blackening solution, but see also any instructions on this. Some solutions don't work well colder than room temperature ie. 20C. As you say when the blackening doesn't 'take' it either goes powdery or flakes off. I think this can be because the chemical reaction is going too fast. I have had some success with Birchwood Casey gun blue on brass, which you paint on and wash off with water, although you have to do a few applications to get any depth of finish. On steel I have been using some chemicals, a four part process, I got years ago from the M.E. exhibition, called METALBLAK from an outfit called Delway Technical Services, although I am not sure if they are still going. Another factor seems to be the age of the chemicals, they do go off after a few years. There are a lot of companies offering blackening kits, just be sure what you get is for the type of metal to be blackened, the main difference being between ferrous and non-ferrous. One further thing is the final finish, most processes recommend soaking in de-watering oil or jade oil to finish. This helps to fix the finish and protect it a bit. One thing I discovered is that blackening doesn't rust proof steel, the oil helps prevent it. The whole process can be very messy and leaves you with all sorts of horrible chemical leftovers to get rid of .
Pictured, Slaters steel tyred wheels and steel buffer heads treated with METALBLAK and dewatering oil. Brass axleboxes treated with Birchwood Casey brass black ( see background ) and jade oiled. The wheels in the background ended up being painted as it took so much chemical blackening them, but I still think the chemical finish is nicer. You can't really see it in the pic but ( disappointingly) the Mansell wheels are starting to rust .
Finally John F you had me puzzled there, but what I think you are looking at is my ancient swivel vice. Bought for me by my dad at an M.E. exhibition many, many years ago, and so very useful ever since, a true third hand. Sadly it doesn't sharpen pencils .
in the pic it reminded me of the sharpeners we had at school ( apart from the anvil ) lovely tool I bought a swivel one it lasted a month before it snapped, they don't make em like that any more.
