fzrburn;
Good afternoon sir, I trust this finds you well on a cool, windy Sunday.
I've been making my own rust bluing formula for a couple decades now and use something quite close to the one in the link below.
http://www.homegunsmith.com/archive/T8338.html
I would be remiss however if I didn't set out a couple of warnings though before anyone makes their own.
First the containers must be glass - jars have worked for me so far - but thick jars are better.
Wear protective glasses and gloves and mix this in a well ventilated area.
Mix the two acids together very, VERY slowly.
I use uncoated nails instead of cast iron chips, but again there is a requirement for a well ventilated area and perhaps a charcoal respirator wouldn't hurt either.... There is an orange/brown gas that comes off when the nails are added and you DO NOT want to breath it.
Anyway once it's mixed it does calm right down and works really well.
I cut mine with enough distilled water so the rust pitting/oxidization is "just right" after 24 hours - so I can work on them after supper and after work. Some of the initial tries might pit the metal too deeply if your solution is too severe off the start.
Store the solution in a plastic container with a plastic lid and out of direct sunlight - it'll last for years and perhaps even decades.
Hopefully that was useful for you or someone out there wanting to do their own rust bluing. By all means give me a shout if you think I can answer any further questions.
Good luck on your bluing jobs whichever way you decide and all the best to you in the upcoming weeks.
Dwayne
