Ran - absolutely go into it. So I had it just backward about the soot and the smooth areas? I don't know if it matters though since once carded they looked about the same.
The problem of handling and maintaining absolute cleanliness can be eased by using Laurel Mountain Forge Barrel Brown and Degreaser:
https://laurelmountainforge.com/barrel_brown.htm It contains a detergent and will allow barehanding( with clean hands) the metal while coating, boiling and carding. This is a huge advantage especially when using a powered wire wheel. A heated damp box is good if you live in a dry climate. 90 deg. F and 90% humidity will produce uniform rust in a few hours. All wire brushes for carding should have wire .005" dia. or smaller. If you use a powered 6" wire wheel, don't exceed 500 RPM. Boil in distilled water. It is cheap and readily available. Low and medium carbon steel like a barrel will usually develop a good blue in 4- 6 cycles. 4140 like a modern receiver will take 6-7 and won't get really dark blue because of the chrome content. The entire coated area should have a uniform black rust coating before boiling. 5 min. is plenty for boiling time. When starting out, always apply the first coat over a freshly polished surface. The reason is that an aged polished steel surface will develop a thin, transparent iron oxide film that inhibits the first coat's chemical activity. Don't want that. A fine( Gray) grit Scotch Brite pad will do the job just before the first coat of blue.
RAN
