The traditional Birmingham bluing tank formula as used for decades.
3 Pound of Caustic Soda (Sodium Hydroxide)
5 Pound of Sodium Nitrate
3 ounces of Sodium Chloride
17 ounces of Trisodium Phosphate
10 pints (UK) Distilled Water.
Bring to the boil to use.
Put a mark on the inside of the tank when first filled and keep adding water to keep the same level as the boiling reduces the water content.
This formula produces that fine Birmingham made gun deep bluish black colour, if the solution looses its strength just add a little Sodium Nitrate to bring it back up to strength.
My personal experience of this bluing mixture is that it is not too sensitive to moderate temperature swings as long it is kept boiling.
***** Do not try to use this to blue vintage side by side shotgun barrels, the liquid temperature is higher than the soft solder melting point that hold's the barrels together and the ribs on. Rust bluing only for them!!!!
