Michael, there are many factors bearing on whether to purchase white
gold (WG) or platinum §.
First you need to understand that there is no resemblence between the
two metals. WG is basically an alloy of gold with copper, nickel, and
zinc, while P normally contains a small amount of cobalt. Because of
the nickel content WG is more suseptable than yellow gold to a
condition known as “stress corrosion” caused by various corrosives in
the environment working on the individual crystals of metal that form
on the surface during manufacture. When a stone is set into a white
gold head, the prongs became prime candidates for corrosion because
they remain exposed to corrosive materials of all kinds, and to
continued stress from being banged against hard surfaces. Over time,
the prongs become very tempered, the individual metal crystals become
etched and therefore weakened and finally the prongs begin to spring
away from the surface of the stone. Inevitably they catch on
something and are bent away from the stone. If the prongs are of
heavy metal and are holding a smaller stone, say, under .5 carat,
there is less exposure and the chances of them being torn away is
lessened. But on a large stone, the prongs are spaced more widely
apart and more exposed. If a prong should become bent, there is less
holding power for the stone. I have always recommended any stone .5
carats and above be set with six heavy prongs when using WG.
With P, the metal always remains soft. It does not corrode, will not
etch or weaken and thus when a prong is bent down to the stone, it
will always remain there. It hardly wears at all so the prong need
not be as heavy as a WG prong but even in a P setting, I recommend
using six prongs from 1 carat up.
The problem for a client is the relative costs because P is much more
expensive than WG.
Questions to consider are, what is the size and quality of the stone
to be set? If it is over .5 ct and of high quality such as D color,
VVS, etc, etc., the extra costs might be worth it. Certainly anything
of quality over 1 ct deserves more protection.
Is it necessary for the entire set to be white? Remember, WG is
whiter than P which is more gray in color. You might also consider
using a P head on either a YG or WG shank if the stone is significant
in size and quality. That way you can save some costs without
sacrificing durability and safety. Hope this helps. If you are still
confused contact me off-line at @coralnut.
Cheers from Don at The Charles Belle Studio where simple elegance IS