Is this just a marketing ploy to sell more product, or is this
really something I should consider?
It’s not a marketing ploy. but it is slightly incorrect. The problem
isn’t so much copper bleeding through, it’s silver, as well as the
gold itself diffusing down into the silver. Gold and silver are
completely intersoluable in each other, and a gold plate directly on
silver, whether sterling or fine silver doesn’t matter, will both
tarnish over time, as silver bleeds through to the top and can react
with the atmosphere, but worse, the thin gold layer diffuses down
into the silver itself, and the color gets paler and paler. In a few
years, it won’t look gold plated any more at all. The nickel
underplate isolates the gold from the silver, and stops this
diffusion of each into the other.
It is possible to avoid the need to use the underplate if the gold
plated layer is exceptionally thick. That will cost you more. It
normally takes more sophisticated plating equipment to do a good job
of such a thick gold layer with a still good finish, and the added
needed amount of gold is a lot more costly than nickel. But if the
gold is thick enough, the silver won’t make it through to the top,
and the gold won’t disappear down into the silver. A simple example
of that is in Keum bo, where thin foil is adhered to the silver.
That gold foil is thick enough for the color to remain permanent, and
it’s about the thickness you’d need to get with plating for similar
permanence. That’s many times thicker than the usual gold
electroplate.
Can Gold be pen-plated onto Sterling and Fine Silver (hopefully,
in a way that highlights, rather than overwhelms the piece) without
risk of a later Copper bleed-through result?
Sure. Use a nickel underplate with another pen first, just where
you’ll put the gold, and then gold plate over that (be sure to rinse
between metals, so as not to mix the nickle and gold, either on the
piece or on pens. Nickel is acid based, your gold, if cyanide based,
would react badly to that… You could try to get a super thick gold
plating directly, but pen platers are not likely to give you a good
enough thickness for permanence. But then, permanence can be a
relative value. How long do you want the plating to last? A year or
two? Then the pen plated layer is likely OK, especially if you take
the time to get it a bit thicker than just enough to color. But if
you want a decade out of it, then the first part of this paragraph
applies.
Peter Rowe