PVD (Physical Vapour Deposition) - Coated Gemstones
These stones have appeared recently. They offer
brilliant colours at a reasonable price, and iridescent effects
which are not available in natural stones.
Identifying PVD - Coated Stones
What are the Benefits?
Repairing Jewellery which Includes Coated Gemstones
The Second-Hand Market
Sometimes we find the owners are not aware the
stones are coated. This is serious because these gems have
introduced some new problems. The coatings have variable
quality. The best are durable, and very unlikely to break
away from the stone. With care, the coating should last as
long as the setting. But read on, and make sure you
understand how to look after these beautiful stones.
Lower quality stones are appearing, and their quality can be
poor. They can be damaged by sunlight, or alcohol
wipes. However we have seen none as yet.
An experienced jeweller should be able to advise you.
Whenever a stone is described with a name you don't recognise,
check it, as often, coated gemstones are sold under special
names. The Internet or a jeweller will be able to help.
Currently most stones treated are topaz, clear quartz and
C.Z. but the market is changing all the time so others may appear.
In the first place the coatings make vibrant colours possible; colours which don't occur in natural stones, at least as a reasonable price. The treatment involves applying an
extremely thin layer of a specific chemical to the stone.
The other popular effect is iridescence, which is achieved by
applying an even thinner layer, often titanium; then
refractions within the layer produces iridescence - it's an effect similar to an oil film on a wet road.
The best manufacturers make sure the coatings are durable and
bond strongly to the gemstone, in addition they choose coatings
which are tough, and which will last as long as the settings,
provided reasonable care is taken.
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Often the coating is only applied to the back of the stone
which reduces the risk of damage. However we cannot be
certain this is always the case. If the stone is chipped
the damage will be more serious than with a normal gemstone as
the coloured layer will be lost at that point. However with
care the coating will last as long as the setting. But
often we see old stones where the back has been chipped, so do
take extra care especially when these stones are mounted in
rings.
Iridescent stones will be spoilt by any scratches. So
these stones should only be worn on recreational occasions, and
certainly not when doing any form of manual work, and that
includes washing up!
Eventually they will need cleaning. It is difficult to
give you the correct advice because the coatings vary both in
chemical composition and in quality of application. If at
all possible contact the seller for guidance; if not follow the advice here.
But understand this is purely advice for which
we aren't charging so we cannot accept any responsibility if
a stone is damaged when you clean it. There is always the risk that poorer quality
stones may appear at any time, which will not be able to
withstand even the gentle treatments recommended.
It's easy to tell you what you must NOT do. Do
not attempt to polish the jewellery; that includes rubbing it
with a jewellery cleaning cloth. Never use an ultrasonic
tank (although you will often get away with such treatment) to
clean it. And acids are strictly out.
To clean, soak the piece in warm water with just a dash of
washing-up liquid. Any stubborn dirt should be removed with
a very soft brush. Is it better to soak for a long time or
use more pressure from the brush? Unless the chemical
composition of the coating is known it is impossible to give
advice.
Iridescent stones need even more care. The beautiful
effect is produced by refraction within the coating.
Anything on the coating will spoil the effect. This
includes grease, either from your skin or from the
washing-up. Even water drying on the stone will leave a
small deposit and spoil it. So dry the jewellery on a paper
towel to absorb the water. If necessary give a final rinse
in de-ionised water.
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These stones will not stand up to the cleaning required after
repairs. So most jewellers will not do any repairs,
including ring sizing.
If a stone is lost or damaged, replacement may be impossible, as
the coated stones are often not available through normal trade
sources. You would have to return them to the original
supplier.
Because there are problems with the stones durability, and
repairs are impractical, our offers are rather
disappointing. After we buy the jewellery, it is cleaned
and polished. So if the stone is low quality, it may be damaged, and then we have
to scrap the piece. That's why we cannot pay
high prices for coated stones.
Our customers can buy with confidence. The stones have been
tested first by the original owner, and then thoroughly cleaned
in our workshop, so they must be durable. The new owner
must still exercise the usual level of caution as described
here. But with reasonable care, the jewellery will have a
satisfactory lifespan. And at our second-hand price, they
are great value.
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