Bright blue, Blueing

[mikeS]

I saw some spurs the other day that were forged steel, and they were a bright blue. The man selling them did'nt make them but thought the process involved lime, slaked or otherwise. Anybody Know?

 

[Fox Creek]

He may have been thinking of the use of crushed limestone as an accelerant in case hardening by the pack method.

 

[mikeS]

How do you do that ?

 

[Fox Creek]

well, this is a traditional method to carburize the surface a few thousandths deep, but as a side effect you can get the rainbow coloration that is so prized on antique and replica guns. Pack polished and clean steel in a iron box with charcoal(supplies carbon), charred leather(supplies phosphorous), and some limestone gravel. bolt top on tightly, heat to red, and hold there for several hours. Quench from red heat to harden carburized surface. that's it in a nutshell. In practice I think it is a lot harder to get the effect. gunsmiths do this mostly. The surface coloration is not durable, but must be protected with lacquer for longest life. Also, in the 19th century when a lot of iron and non-hardenable mild steel was used for firearms(rendering questions of tempering moot)steel parts were "heat blued" by simply baking at a low temperature until the surface oxidizes blue, just as if you were tempering to a blue color. This is supposed to be a bright peacock blue obtainable no other way. I've seen photos of old gins, etc. treated like this, and it is a beautiful color. But again it is not too durable, just a surface effect. "Hot salt" bluing or "rust" bluing is much more durable and actually gives some protection to the surface from corrosion.

 

[Darrel Ralph]

For The cased look bring the oven to about 1450 for . Pack the parts in BONE charcoal
Put them in the oven for two hours
The dump the whole mess in aggitated water.
An little air pump will do fine. Make sure there is enough water to make the parts cold by the time they hit the bottom. Add some burn leather also if you wish.
The other way to get blue blue us nitter salts ... Brownells has them This provides a REAL BLUE BLUE...


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[mikeS]

Thankyou . I appreciate the time you took for the answer.