There has been a somewhat lively discussion on Orchid concerning as to whether the tarnishing of silver will affect the colour of a diamond set in that material.
On the one side were those that said no, using optical properties of diamond as an argument, and on the other side were those who said yes, using the experience of working with antique silver jewellery set with diamonds as their argument.
However, to me this stuff is not rocket science, and I don't write a million words about it.
I just do the work and take pictures. Much easier.
The tube , normal silver.
The other tube blackened with Liver of Sulphur.
The two diamonds set. Both diamonds are Colour "G" VS stones. The blackened tube is always on the left in this sequence of photo's.
The tubes, polished as one would do normally and the cleaned in a ultra sonic cleaner, rinsed and blown clean with compressed air. The diamond on the left is markedly darker.
Then, to be completely fair, I set two diamonds in tubes without first pre-blackening one tube.
I use a punch like the one shown to set stones up to 5mm in diameter in tubes.
So the diamond on the left was blackened AFTER being set.
After polishing and cleaning, the diamond on the left is still darker than the diamond on the right.
Conclusion: Jewellery that is tarnished can affect the colour of a diamond set in it.
However, I doubt very much that a stone set with prongs will have much of a difference in colour. ( less metal touching the stone)
I also suspect that if the diamond is large, like say 7mm in diameter, the tarnishing would have less of an effect than it does on a smaller stone.
But any jeweller that sets a large diamond in silver should probably go back to school.