Cold Bluing Formulation
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Q. Can anyone please assist me with a better formulation and process for "Cold Bluing".
The one I currently have is as follows:
Copper Sulphate 10 %
Selenious Acid 6 %
Nitric Acid 5 %
Demineralised Water 79 %
I am an industrial chemist and am familiar with the hazards of metal finishing chemicals in particular. Regards
Industrial Chemist & Registered Gunsmith - Western cape, South Africa
January 22, 2008
A. Cold blue:
manganese nitrate...50 gm (up to 75gm)
copper nitrate .....50 gm
50 °C temp.
Hope it helps and good luck!
- Zagreb, Croatia
January 22, 2008
The formulation you have is about right for a "cold blue". As you would guess it gives a bluish finish of copper selenide. It is quick, easy, cheap and pretty useless for a working gun.
The durable finish you need comes from a molten caustic / nitrate bath. It is nasty, difficult, potentially dangerous and gives a superb finish.
September 12, 2020
Q. Hi I found this recipe on this forum and am using to blue steel which will be clear powdercoated for decorative use, could you please help me with the best method to combine these ingredients?
Copper Sulphate 10%
Selenious Acid 6%
Nitric Acid 5%
Demineralised Water 79%
- Invercargill Southland
A. Hi Shayle. I have no experience with the best sequence for mixing those ingredients, but do have two comments. First, I'm not confident that good adhesion of the clearcoat is assured, because these formulations do tend to be smutty. Second, if you're going for blue, you might need highly polished metal; I believe that selenium blackening treatments tend to look a dark jewel blue color on highly polished metal but matte black on rougher surfaces.
Luck & Regards,
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading