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Pine Beach, NJ

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Blackening using ammonia nitrate without sodium hydroxide

February 29, 2012

Q. I am a retiree trying to blacken soldered shotgun barrels. Reading various articles about this subject, people seem to think that sodium hydroxide is only used in the ammonium nitrate mixture in order to elevate the boiling point and has nothing to do with the blackening.

However, I have tried this using pressure to elevate the temperature, thereby eliminating the lye, which is undesirable as it eats the solder. It did not blacken the metal. Is there anyone on this earth that really understands the chemistry enough to tell me why?

John Rowe
Hobbyist - Dartmouth NS Canada

Try to iron plate soft soldered parts and then try to colour it with black oxide. Without oxidizing agent (ammonium or sodium nitrate ⇦ this on Amazon [affil link] ) black oxide can't work. Hope it helps and good luck!

Goran Budija
- Zagreb, Croatia
March 5, 2012

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