I’ve used 18 and 14 karat green gold in my work using wire and
casting grain from Stuller and Hoover that I cast myself and castings
from well regarded casting houses and I can tell you that in addition
to being a soft metal that doesn’t work harden, it’s also prone to
tarnishing. That’s the nature of the metal.
Polished 18 wasn’t problematic, but any kind of non polished texture
on 18 green, whether it’s added or on a remaining raw surface from
casting, it will tarnish over time. Textures I’ve used include
lightly brushed matte, heavy grit sandpaper, fine and coarse
sandblasting and stippling. There are environmental factors that will
hasten the effect, like cigarette smoke and exposure to LOS, but even
in normal conditions, over time textures and areas not exposed to
wear in 14 kt green alloys will tarnish.
A single cycle in an ionic cleaner removes all traces of color. The
plus side is that after the piece goes through several
tarnish/stripping cycles, you’ve in essence created an enriched gold
layer that is much more resistant to tarnishing.
Since gold prices increased I no longer make these prices, but the
color was really beautiful and contrasted well against yellow, red
and white gold.