Oil of sulfur

[F.G. Ford]

Can anybody tell me what "Oil of Sulfur" is?
I have been told that it will turn copper black,
not unlike blueing solution on steel.
Any help would be appreciated.

Best Regards

Old Ford

 

[lockjaw]

...you mean "liver of sulphur"... smells like rotten eggs... look here

 

[benvenuto]

"Oil of sulfur" is sufuric acid if I recall right...
you want "liver of sulphur", available from any jewellery supply house. my local place sells small quantities, but they did warn me that it loses its potency over time or if exposed to light (comes in a black plastic vial)

 

[paulvallandigham]

Why not just use a paste made of some black powder and water, and put that on whatever copper you want to turn black? I assume you are trying to " age " some piece. the sulfur in the black powder is more than sufficient to do that task. Just my 2 cents.

 

[bwhoffman]

I have had good success using the dirty patches after wiping the barrel and then wiping the brass on my rifle.
Leaves a nice patina, considering I dont really like the shiny brass on my guns.

fwiw,

Brett

 

[DrTimboone]

My experience with liver of suphur is that it dulls the brass rather than blackening it. I treated mine with it and then after it was dry I wiped gunpowder residue on it...can't seem to make the water/gunpowder paste work. :redface:

 

[Norskie]

Sulfuric acid was called oil of vitriol. Could also have been called oil of sulfur, but I have not heard that term. Hmmm

 

[paulvallandigham]

Leave the sulphur on the brass long enough and it will turn black. I suppose this might vary depending on the mixture of tin, copper and zinc used to make the brass. It is the softer copper that turns black.

 

[Stophel]

Some people use eggs (yolks) to blacken brass. :winking:

 

[paulvallandigham]

And eggs stink because the yolks contain sulfur. Sulfur and water makes Sulfuric acid. It does not matter where you get the sulfur, as long it combines with water to make the acid. The strength of the acid will determine how fast it oxidizes the brass, and how deep the surface will be etched.

 

[brubincam]

as CURLEY would say...YOLK YOLK YOLK... :youcrazy: :youcrazy: :youcrazy:

 

[Stophel]

Oh, a wise guy!

 

[Mad Professor]

The main thing that gives eggs, rotten or otherwise the smell/stench is hydrogen sulfide (H2S), a volatile toxic gas. It reacts with many metal cations (e.g. Copper, Cu +2) to produce a black solid precipitate. I've used it in schemes to separate/identify mixtures of metals which have been digested (oxidized) with nitric acid to produce soluble cations.

I'm not sure if H2S is the best way to blacken copper/brass. I've seen several "recipies" which employ ammoinium carbonate and copper sulfate: Henley's Formulas for Home and Workshop (G. D. Hiscox Ed.: Anvel Books: New York, 1979) gives several "recipies" that are decribed as a "finish" rather than just a discoloration for brass/copper. The most "PC" of these is a referenece to using conc. ammonia with the ore Malichite.

I can give more details if you're intersted?

 

[Mad Monk]

Mad Professor,

BP residue will stain brass brown to black via the potassium carbonate in the powder combustion residue.

I have several pounds of tech grade potassium carbonate. To darken brass I'll dip strips of paper towels in a solution of water and "potash" and lay them on the brass. Brown smudging or black depends on R.H. at the time.