Sterling Silver Patina
Q: How do you use liver of sulphur to patina sterling silver?
A: When mixing liver of sulphur for bench use, I find a ¼ to ½ inch sized chunk is more than enough for the two cups or so of water I dissolve it in. The trick is to use it heated. At the least, it should be a bit too hot to touch, but any temperature up to the boiling point works well with straight liver of sulphur. If you’ve got ammonia in the mix, (which some people like to add although I find it leaves a filmy deposit on the patina), boiling it gets too smelly, and seems to degrade the solution quicker.
Since liver of sulphur solutions, once mixed up, have a shelf life of only a couple of days maximum, it’s best to use it in a manner that uses as little as possible for each batch If you notice that the patina flakes off, you’re using too strong a solution, or leaving the metal in too long. Generally you should make sure that you have a clean sound metal surface before you put the piece in the solution, with no scale or the like to interfere with the chemical reaction. Use liver of sulphur in a weak enough solution so that it takes a moment for the patina to develop. Watch it carefully, and remove and rinse as soon as it’s fully black. Longer than that won’t improve the durability of the oxide coat, in fact if the layer gets too thick it will just flake off again.
If your piece turns black before you can blink, rather than grading through the colors at a speed you can see, it may be too strong. Rinse the piece as soon as the color is sufficiently dark for your taste, and the reaction will stop. If you like the matte dark black of the just applied finish, you then have to be quite careful in polishing up the highlights so as not to hit that surface at all. It will quickly buff off and you have to start over. Once you’ve gotten the piece looking as you like, a coat of wax (Renaissance Wax works nicely) will help protect it from casual abrasion. Normal atmospheric contamination will also tend to keep the finish “renewed” in non-wear areas.
Personally, I prefer a higher sheen to the oxidized areas, and use a fine brass plater’s brush and soapy water, or a rotary brass or nickel-silver brush on a slow arbor going about 150 rpm, using soapy water as a lubricant, to brush it down after the black surface has developed. This burnishes it to a lighter blueish-black color. I repeat the entire application at least twice. The result is not a matte dark black, but a blued steel sort of look, burnished and metallic. That surface, due to the burnishing action, is considerably more durable than the original matte black color, though it has less color contrast.
I often use that finish on an entire silver piece, with very little highlighting. I’ve generally found that this surface doesn’t need the wax coating so much. Also, the brass scratch-brush gives a wonderful finish to the silver all on its own. If you’re using it on non-darkened silver, use the nickel-silver versions of the brush, rather than the yellow brass ones. The brushed surface (remember, slow and lubricated) is a very uniform high sheen, but not polished. The surface is not directionally scratched, as it would be with those Scotchbrite satin wheels (which are a much, much coarser finish than this one) Like a polish, it’s reflective and elegant, though you cannot see your face in it. The shapes and forms of your work actually show up better, as you see the actual silver surface, not just reflections of everything around it, and if you happen to have some fire scale (you shouldn’t but after all this is the real world) still in the surface, it shows up a whole lot less under this scratch-brush finish than under a true polish. Unlike a polish, it doesn’t instantly show the first fingerprint to touch it, and will look the same after handling and wear as before. It seems to me a much more practical surface for silver that’s actually to be used.
By the way, using this finish is not an excuse for not polishing the surface correctly. For the best effect, the surface should be properly and conventionally polished out to at least a white diamond compound (you can skip the rouge) before scratch-brushing. Then, after scratch-brushing, oxidize the piece if you like, scratch brushing/burnishing in the oxide surface. If you have trouble getting a uniform color, you can even apply the liver of sulphur (hot) with the brush as well, which seems to help. (rinse it well afterwards). The scratch-brush, used wet, won’t remove the black, only burnish it. Then the final step is to rouge those areas desired as bright highlights, or use white diamond if you want to remove the oxide on larger areas. You can then proceed to either rouge-polish or scratch-brush the now white areas again.
by Peter W. Rowe M.F.A., G.G.