[UncleFester]

Hi - I'm looking for a way to turn lead split shot (used for fishing) a dark grey or black using easy obtained household chemicals. I think what I want to do is create a layer of lead sulfide on the surface of the shot.

I've been experimenting with various combinations of vinegar, hydrogen peroxide, HCl (Lysol Toilet Bowl Cleaner), sulfuric acid (SureShot drain cleaner), epsom salts (magnesium sulfate), and a 12 v battery, but so far nothing works.  Some of the acids seem to turn the shot white, which I take to be lead oxide on the surface?   And the battery current+Epsom salts+HCl did produce lead sulfide but not on the shot, just on the copper wire that was connected to the battery. The shot actually started to get plated with copper, looked like. I also tried a mix of shampoo and sulfuric acid to generic hydrogen sulfide (small quantity, outside for safety) and it made the shot dull grey but not black.  I know of a commercial product containing nitric acid, selenium, and copper sulfate that supposedly works instantly.

The process objectives are: needs to work on a few tablespoons to 1/3 of a cup of shot at a time. And hopefully the only equipment needed will be a glass jar, some solo cups, a plastic fork, etc. And should take no more than 24 hrs (though longer would be OK, just not as convenient).

(I worked in a research lab for several years and know how to work with acid etc safely....). 

[curiouscat]

Why not use paint?

[UncleFester]

Why not use paint?

Paint would probably work, but falls short of an ideal solution because
1. Paint would probably chip off as the shot were rattling around in my fishing gear over the course of a season or two.
2. Would be a pain in the butt to cover the shot uniformly.. have to shake/turn them several times
3. Paint might clog the slit where the line goes, or cause the sinker to slide more than is desireable.

My latest trial is to put some shot in an empty wine bottle, toss in several lit kitchen matches, and cork it up. Hopefully creating a low/no O2 reducing atmosphere. 

[curiouscat]

Coal tar / asphalt?

Alternatively molten India rubber?

Or Carbon Black?

[curiouscat]

The shot actually started to get plated with copper, looked like.

Could it have been Lead tetroxide and not Copper?





If so, try then adding Nitric Acid:

Pb3O4 + 4 HNO3 → PbO2 + 2 Pb(NO3)2 + 2 H2O

PbO2 ought to give you the blackning:

[Arkcon]

Lead sulphide is black.  Exposing the lead pieces to H₂S vapors would work, but they're not easy to get.  Perhaps just leaving them in sulfur powder will eventually darken them.  You can sometimes by a sulfur candle for fumigation at the hardware store.  And maybe the drugstore has flowers of sulfur.

[fledarmus]

Look up patinas for metal working or jewelrymaking. One of the most popular and oldest black patinas is a solution of liver of sulfur (a mixture of potassium sulfide) in water with a some ammonia. Makes a nice black on sterling silver or copper, somewhat slower on fine silver. I've never tried it on lead, but I don't see why it wouldn't work. You do have to wash your starting pieces to remove any traces of oil or wax that might be on them

You can buy the solutions premade at most jewelry supply shops, or buy the liver of sulfur and make your own.

[UncleFester]

OK - so some new web research has turned up suggestions that a vinegar soak or salt water bath followed by drying in air will produce a nice dull grey finish. And also that storing the lead shot in a baggie with water present will cause the formation of a white coating - lead oxide. And that storing the shot with some silica gel to absorb moisture will prevent the formation of PbO.  Does all this make sense in terms of the chemistry involved? Can someone explain it for me?  Fundamentally what causes the metal surface to be shiny vs. dull?