Ah, it's just me not understanding what to expect then. I was expecting the conversion to be just a hard black substance. The first time I boiled, much of the surface area just turned black and only about 40% or so developed this soot, so I thought the hard black areas were the norm, not the sooted areas.
You should have a uniform coat of "soot" over the entire area you coated with the rust blue solution. If not, you are doing something wrong. Most likely the metal was not clean enough in those areas that did not develop the soot, but I'm guessing. The metal must be chemically clean before coating with the blue and must remain that way while boiling, carding, and recoating as you go thru the process. Most over the counter rust blue solutions cannot cut through the skin oil in a fingerprint and rust will not develop properly. There is a way around this problem, but I won't go into it unless you want me to.
RAN
