How do I mark my PMC work?
All versions of PMC are fine silver and can be marked accordingly. The preferred designation is .999 which is scientific shorthand for nine hundred and ninety-nine percent pure. This is the same designation for pure gold: the two don't conflict because the color difference is obvious. When we write about these, we use the terms, Au 999 for gold, and Ag 999 for silver. You can stamp after firing, but in that case you'll need a metal stamp and those are a bit pricey. If you stamp or carve the numbers before firing you can use a plastic stamp or a needle.
Do I need to mark my work?
Technically speaking, work sold across state lines must be marked with a hallmark and maker's mark, though I've never heard of this being inforced.
What is the difference between a hallmark and a quality mark?
No difference; they refer to the same thing, a designation of the metal or alloy used in the piece. The other thing you might see is a maker's mark, the initials or logo of the artist or company that made the work.
How do I use a tumbler to clean my PMC?
For the record, the tumbler is not used to "clean" your silver work, but to burnish it. Burnishing is the process of rubbing a soft material (in this case silver) with a harder one (steel), in order to make a compressed surface. In the case of PMC and steel shot, the result is shiny silver.
You want to use polished steel shot and enough solution to cover the shot plus about a half inch. The best solution is a commercial product made just for this purpose. It is sold by all jewelry companies that sell tumblers, and it is quite cheap. It usually comes as a concentrate--a $10 bottle will make many gallons of solution. In the short term, you can substitute JOY dishwashing soap for solution. Use about a teaspoon to a quart of water.
I recommend using a milk jug or similar plastic ware for this purpose. Mix up a gallon at a time and you'll be all set. The other useful tool is a plastic strainer or colander. After each use, pour the shot-and-silver into the strainer over a sink so the solution is discarded. Rinse the work in running water, then pull out the jewelry. Put the shot back into the tumbler drum and cover it with enough solution to be sure it will not be exposed to air where it will rust.
Can I use a buffing machine on PMC?
When it comes to PMC, though, work needs to be burnished before polishing, and usually I find that the burnishing provides all the shine I want. If you were to skip the burnishing stage and move directly to a rotary polishing buff, you would find that the polishing compound cakes into the microscopically prickly texture of a PMC surface. Instead of being polished, the piece will appear dirty. Not what you want!
What is pickle, and how does it work with PMC?
Original PMC absorbs pickle, which will then leach out to form blue-green crystals. The solution is to boil (or use an ultrasonic) with a neutralizing solution of baking soda. So you did exactly the right thing. As your experiment showed, the other versions of PMC do not absorb enough pickle to require the cleaning phase. The only thing I can add is that it's possible to avoid pickle altogether, which is my preferred solution. To remove oxidation, I use very fine abrasive papers (or powdered pumice for textured areas). The other reason jewelers use pickle is to remove flux glass, but this will also dissolve in hot water, so I just boil water as if for tea, then pour it over the piece to remove flux residue.
Why is liver of sulfur sold in rocks instead of as a powder?
How do I mix it up? How long will it last?
How do I dispose of it?
Liver of sulfur can be degraded by light, air, and moisture. Exposure to any of these will shorten the potency of the chemical, so it's difficult to estimate how long the pebbles will last. This is the reason that the rocks are sold in relatively large sizes. Exposure will work from the outside inward--if you have a pebble with a crusty pale yellow exterior, you can break it open and usually find a potent, yellow core that will still make a usable solution. A mix of liver of sulfur solution lasts no more than a couple hours, so I mix a fresh solution every time I want to color metal. The mixture can be safely poured down the sink, though I'd recommend flushing it with running tap water for a minute, just to make sure the solution (and it's perfume) gets pushed all the way down the pipes.
How can I preserve patina colors?
Some metals, such as pure gold or platinum, do not react to the chemicals around them, but they are the exception. Most metals react with their environment, which is what produces their color. In choosing a particular patina we are singling out one point on a continuum and trying to preserve it.
If this change is undesirable, the metal must be sealed off from the environment. A hard film such as lacquer will resist marring but can eventually be chipped away. A soft film such as wax is more likely to be vulnerable to wear but will probably just smudge across the protected surface, keeping the film more or less intact. In articles to be worn, wax can rub off on clothing.
If I was going to do anything, I'd carefully apply several very thin coats of spray acrylic (art supply store; ask for fixative). But be aware that a layer of anything, even something perfectly colorless, will alter the way light is refracted, which is what gives us the colors in the first place. In other words, the very act of adding a protective layer changes the colors.
On the positive side, I've had good luck with keeping the liver of sulfur colors even without protecting them by keeping the work sealed in a Ziploc plastic bag when it is not being worn.
How permanent is liver of sulfur?
Liver of sulfur is quite permanent in areas of a design that are protected from abrasion, like recesses. In those areas it will stay black for many years. In exposed areas that are subject to wear, like the outer surfaces of a ring, liver of sulfur will wear off in a week or two.
An alternate product called Silver Black is a bit more permanent, but will also wear off if exposed to abrasion. The primary advantages of Silver Black are generally that it is instant and a bit darker than liver of sulfur.
Putting a protective layer on either patina is not really going to help, since it is not just the black that wears away but the silver itself. Silver is assigned a value of 3 on the Mohs scale of hardness (a scale of 1-10 in which a low number can be scratched by a high number). Quartz, which constititutes 90% of the dust in our lives, is 7 on the scale, so simply rubbing your dust-laden finger over any metal is like using sandpaper. Varnish or wax would not improve the longevity of the patina.
Both Silver Black and liver of sulfur are sold by jewelry suppliers. Note that Silver Black is acidic and should be kept away from kids and pets.
