On Tuesday, October 30, 2018 at 5:38:43 PM UTC-4, Mike Spencer wrote:
writes:

To create contrast, I used an oxy-acetylene torch to heat patina my
background after cleaning it with an angle grinder. The patina came
out really nice, with brilliant blues and magentas.

The problem came after I threw a little Renaissance wax over the
patina: all the nice colors were lost and the foreground and
background basically look the same. I saw one post online that said
those colors cannot be clear-coated because the optic properties are
lost, but it recommended waxing.

Is there any good way to get those colors back? If I remove the wax,
are the original colors hiding beneath? Or will I have to repeat the
heat? In either case, is there a good way to protect the metal without
losing the colors?

My experience is that those heat-induced "temper" colors are too
fragile and ephemeral to be relied upon in any practical application.

Years ago I made some nice belt buckles, mild steel inlaid with brass.
Skipping over numerous details and difficulties, I was able to get
really nice heat-induced blues on the polished and carefully cleaned
steel, lovely contrast with the brass. But they didn't last. A
droplet of water/moisture would remove the color. Coatings changed
it. Wear removed it fairly quickly.

The blue tones created with various gun bluing techniques are
different, darker, less exciting, but far more durable. Brownell's
OxphoBlue(tm) is one I've used a lot but tends, with aging, to nearly
black.

There is a bluing technique using molten potassium nitrate reputed to
give a better/nicer color but I've never used it or seen the result.
You might research that with gunsmiths or, perhaps, makers of fancy
spurs in the US southwest.

FWIW,
--
Mike Spencer Nova Scotia, Canada

To get a thicker coating with heat, the traditional method (used a lot on guns, 100 years ago) was to heat the steel in the presence of a cyanide-based case-hardening material.

Yes, it's potentially dangerous. And it works. If you use a powder, you get the mottled colors common on Stevens rifle and many shotgun receivers.

There are other ways to do it, but I've long since forgotten what they are. Maybe a search on "heat treatment colorizing" or something like that will bring it up

--
Ed Huntress