[TheForge] Gun blue finishing

[Andrew Vida]

Mike Spencer wrote:
>> Put the piece in a slowly rising toaster oven till it turns
>> blue..slower is better...surface prep is critical.
> 
> I did some inlayed belt buckles like that.  Polish, clean, heat very
> carefully. Result is a beautiful peacock blue.

	The hue is often related to the depth of the oxide layer.  That peacock 
blue, which is a lovely color, is very thin - possibly measured in 
angstroms, given its electric character.  That would be what is commonly 
referred to as an interference color.
> 
> Two problems arose:
> 
> The blue isn't very durable. Without a protective finish (or after the
> finish has worn off) a single droplet of water will remove a spot of
> blue if allowed to remain for a while.
> 
> And I didn't think ahead on the brass inlay.  Used a lubricant to cut
> the inlay dovetails.  When the "clean" piece was heated to get the
> blue, wax boiled out from under the inlay.  Boiled that one in lye for
> a while, reblued.  After that, I boiled them in lye *before* hammering
> in the inlay wire.
> 
> I've read about a bluing process that involves immersing the workpiece
> in molten potassium nitrate and sodium nitrate.  Anybody have
> experience with that?  IIRC, it was being used on spurs for drugstore
> cowboys.

A hot blue process, which is a different kettle of fish.  Great care 
must be taken because hot caustics like that will wreck your day in a hurry.

Also, hot blue often does not produce as good a result as cold, - IOW it 
is easily botched - though I have seen some hot blue work that was 
excellent - the early Colt Pythons had some of the best, deepest, 
cleanest hot blue ever.  Hot bluing generally produces a thicker, deeper 
looking blue.  The hazard there is that the surfaces can take on a 
slurred look - runny lines on surfaces almost as if it was a bad paint 
job.  But when done right, hot blue can be fab.  My assassin's rifle, a 
very trick '98 in 270, has one of the most fabulously well done hot blue 
jobs I have ever seen.

For larger work, it seems to me that cold is the way to go.  The fixed 
investment in equipment and salts would only make sense if you were 
going to be doing a whole lot of big items.