These are some recent 1911 parts I Nitre Blued at the shop. Nitre Bluing creates an array of colors from deep blues and purples to a pale yellow. Depending on the temperature of the salt bath.
I love the nitre blue colors, and last year was thinking about ordering the salts and heater. But then I found out that the required very high temperature basically ruins the heat treatment of the parts -- that's why you only usually see it on very low-stress parts like screws. Dreams shattered by the realities of metallurgy.
The finish is not as durable as a conventional hot blue. Typically nitre bluing has been used on accent parts that don't receive a lot of handling. But if you take care of your things they will last a long time. There are still guns from the 1800s with original nitre blued parts in excellent condition.
Nitre bluing will not ruin the heat treatment on parts at the temperature and time it takes to blue a part. A nitre bluing bath can be used to temper steel at 650 degrees. But even at that temperature it would take a 15 minute soak to temper a tiny spring. The parts being blued are in the bath for a matter of seconds to reach color.
These aren't going on a specific build. These were just a couple parts I ran extra to sale as I was bluing other people parts they sent in for this finish.
I typed the title into my smart TV in youtube and it said there was no such video, which obviously isn't true because it plays on my PC. The other link's title worked though. Maybe caused by alien beings?