Rust bluing, from what I have learned over the many years, is not real difficult once the prep work is done, and that is a BIG thing. Just as in stock finishing, everything done to prep for finishing determines the final product.
I have seen rust blue jobs that were so thin it could have been said they were not even halfway finished. Light grey with sanding underneath still showing. Others were so rich and dark, regardless of hue, they had depth and patina that shouted.
It seems that some doers of this art do not use the best rusting solution, do not let them rust long enough, do not boil in clean distilled water properly, and do not card the barrels correctly to achieve the depth of color that really shows a true high-quality end product, but that's only a guess having never done it myself. I just know that when you've seen it done right, you know it, and vice versa.
JR
