[TheForge] Re: Gun blue finishing

[Mike Spencer]

I've had great results with Brownell's Oxpho-Blue. [1] I don't recall
the names of the other bluing products I've tried but they were all
harder to use and produced poorer results.

The workpiece doesn't have to be absolutely perfectly grease free
because, as advertised, acid in Oxpho-Blue cuts through minor stuff
like fingerprints. Of course, phosphate pickle or bead/sand blasting
followed by no soiling of any kind is the best guarantee.

A consideration that I hit was removing mill scale.  In a piece with
both forged parts and panels of unworked sheet, the sheet is likely
covered with mill scale, which doesn't take the bluing at all.
Pickling mill scale off is difficult.  Sand blasting works but mill
scale is tough so bead blasting takes extra time and media.  An angle
grinder, regardless of the media, leaves typical, horrible marks that
the blue does not cover.

My solution to that has been an abrasive wheel (e.g. 3M Clean-n-Strip
or equivalent) of the type such that you use the edge of the wheel.
If you're careful, this leaves linear striations (nor curved ones)
that can contribute agreeable (or at least acceptable) texture to flat
panels.  The 3M product (similar from Walther) cuts through mill scale
adequately, leaving a surface ready for bluing.

Oxpho-Blue is available from 4 oz. up to gallons.  They won't ship
outside the US due to hazmat restrictions. A local gunsmith kindly
carried a couple of pints across the border for me. That probably
isn't enough to do a whole ship or even a boxcar but it's more than I
expect to ever use up.


[1] http://www.brownells.com/.aspx/pid=1072/l=y/Product/OXPHO_BLUE_reg_

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^