As I mentioned previously I am having diamonds go black on me when I
am rhodium plating. They are fine during working and then electro
cleaning but going black in the plating. I have changed my solutions,
cleaned the anodes. It doesn’t happen to all the stones, just some.
Even if there is no metal behind them. I have never seen it before, I
just can’t figure it out and it is nearly impossible to get off. I
don’t know what to do because it seems to only happen to ring I get
from the trade/retail and not mine.
This is just a stab in the dark, but some diamonds are coated with
something (I forget the name) to improve the color. The rhodium may
be interacting with this coating causing the black color. I do not
use rhodium plating much, so I have not run into this problem and I
don’t know how to fix it. Best of luck and if you solve the problem,
please let us know…Teddy
As I mentioned previously I am having diamonds go black on me when
I am rhodium plating. They are fine during working and then
electro cleaning but going black in the plating.
As Leonid asked, are you sure they’re diamonds? But I’d also wonder
whether you’ve encountered coatings of some sort, or an acid
sensative fracture filling. There’s no reason I know of why a normal
diamond would react to rhodium plating solution, so something else
must be at play. Most likely, what’s turning black isn’t normal
diamond. The only other thought is that a very small percentage of
diamonds, those with boron as an impurity (which makes them blue or
grey) are semiconductors. That makes me wonder whether such a stone
might be able to attract a light rhodium electroplate. But the much
higher electrical conductivity of the metal itself would make that
unlikely, I’d think.
I would also be very interested to see if anyone else has an answer
to this one as this has also happened to me in the past. I also
replied on your previous thread and mentioned that when this has
happened to me it is only the stones set into holes that had a
drill-bit stuck or broken in it. I would also like to know why this
would have this effect on the diamonds which seem to end up with a
coating over them. it is very hard to remove… The stones that I
have had changed to a deep brown and a yellow. Very distinctly
different from their true colour. It was only removed by placing the
ring in a strong acid solution and then re-polishing. Any clues??