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Antique diamond repair


#1

Help! I have had one of those dread jewelry disasters and broke a
customers stone. Split right down the middle, perpendicular to the
table.

The stone in question is an antique diamond, that is an asymmetrical
cut and foiled on the back. It measures about 7 x 6 mm and is
roughly a pear shape.

With a diamond wholesaler as a middleman, it was seen by a re
cutter, who refused to work on it. He said it had too many internal
fissures.

We were hoping to have it cut into two smaller, free form stones,
more or less marquise cuts, but with that same antique, foiled back
style. We always hear about sneaky ways of filling diamonds to make
an inferior stone seem much better. Are these kinds of techniques
available when you need help to repair or salvage a stone with
important family and sentimental value?

The customer has been wonderfully understanding, so far. I really
want to make her project as well as I can, but the whole concept
depends on being able to use this stone.

Stephen Walker


#2

Hello Stephen;

Help! I have had one of those dread jewelry disasters and broke a
customers stone. 

Miserable to have that happen, but it goes with the territory. I may
have something like that, I’ll take a look tomorrow. Meanwhile, I
know a guy in NY who works with antique cuts. There may still be
nothing that can be done with the stone in question, but my guy may
have a replacement if I don’t. Email me off forum, I’m at my home
computer and don’t have the info handy, but I’ll bring it home
tomorr


#3

Stephen- A sticky wicket indeed. Is the stone actually in two pieces?
If so, you don’t have many alternatives. Super glue won’t really
help.

Trying to reproduce an old style cut is truly difficult. You might
contact another diamond cutter. Rich Shatz in New York is a dealer
who specializes in old cuts.

If the stone is just cracked but still intact, you might be able to
have it “clarity enhanced” by one of the companies that does the
glass filling of imperfect diamonds, such as Yehuda. The Leshem
website (www.leshem.com) offers clarity enhancement services.

Regardless, I suggest you be sure to get some clarifications and
limits of responsibilities in writing, etc before you do anything
more. Remember the story of the Tar Baby.

Jim
Jim Sweaney
www.mardonjewelers.com


#4

Try Oved diamond in New York they clarity enhance diamonds and I am
sure that the can recut as well. If you have a hard time finding them
call me during business hours and I’ll give you the number.

Good Luck.
James Kallas 505-986-1955 Mtn. time


#5

At the risk of looking ignorant, I’ll say that I’ve never heard of
or encountered a foil-back diamond. I did a Google for it and found
an old Georgian ring that said it had them, and they looked like
diamonds. I also found an “expert” on a forum who also said he’d
never heard of them. Not meaning anything except that I’d test the
stone first off to make sure you’re not replacing glass with diamond
before doing anything. I’m sure they exist and I’ve just never seen
one, but it’s uncommon.

http://www.donivanandmaggiora.com


#6

Hi John;

I thought Stephen was talking about an old rose cut. Flat on the
bottom, rather shallow, with a simple faceting pattern on top. I’ve
seen these set with tin foil under them to act as a mirror, as
they’re rather uninteresting without something reflective. Tin
apparantly was the choice because pure tin is very resistant to
tarnish. I’ve seen some rather large stones of this type, as I work
on a ot of estate stuff.

David L. Huffman


#7
At the risk of looking ignorant, I'll say that I've never heard of
or encountered a foil-back diamond. I did a Google for it and
found an old Georgian ring that said it had them, and they looked
like diamonds. I also found an "expert" on a forum who also said
he'd never heard of them. Not meaning anything except that I'd test
the stone first off to make sure you're not replacing glass with
diamond before doing anything. I'm sure they exist and I've just
never seen one, but it's uncommon. 

I’d assume the phrase referred to something that used to be done
sometimes with rose cut diamonds. These stones, being essentially
facetted cabochon shapes with a flat back, don’t reflect light back
to the viewer from pavilion facets, since they have no pavilion
facets. Light goes right through them, and if there’s something
behind them that’s reflective, the light bounces of that surface and
back through the diamond. So to take advantage of that, some antique
work used bits of reflective metal foil, sometimes even colored foil,
placed in the cavity behind the diamond. it’s not attached to the
diamond, and often not actually attached to the area behind the
diamond either other than by friction or being simply trapped there.
The method is old. Described by Cellini in his treatise/autobiography
from the renaissance, and I’d guess it goes back farther than that by
quite a ways. Colored stones too, sometimes were treated this way as
well. Now, most of us would simply polish the metal surfaces behind a
stone, like a bezel cup or the like, if we wanted this effect. But
polishing those surfaces well before the introduction of rotary tools
like flex shafts, would have been more difficult, and simply putting
in a brightly polished bit of foil would be easier by far. Plus it
could be a different metal color than the setting. Thus a white
reflective surface behind the diamond in a yellow gold mounting
becomes easy and doesn’t need rhodium plating to do… I recall one
antique piece from the early 1800s that I had to repair, and found
what sure looked like a foil behind a rose cut that had been actually
painted/tinted with something to give a colored foil. At least that’s
what it looked like. A pretty pale pink color on what was still a
bright slightly matte surfaced foil of some undetermined metal
stuffed in the back of that bezel cup shape…

With all that said, the term foilback as it’s currently used,
usually means a glass imitation to which a classic mirror back
coating has been applied. I don’t think I’ve ever heard of that
method of actually coating a diamond with a reflective mirror coating
being used.

Cheers
Peter


#8

John,

At the risk of looking ignorant, I'll say that I've never heard of
or encountered a foil-back diamond. 

You’re one of the least ignorant on this list, but foil backs on
diamonds do exist. I’ve come across a few over the years but the
most notable one was very recently when the Isabella Steward Gardner
Museum brought over a few pieces for me to identify some stones on.
They were late 18th century Indian (not American) matching bracelets
with different stones across the top. All of them, including the
center diamond, had various types of foil backings behind the
stones. Many of the backings were colored as well. There was a piece
of “emerald” that had a green foil backing. It was actually beryl,
but almost all of the color came from the green color in the backing.
Quite fascinating to handle such antiques. The museum employees who
brought them over wouldn’t even touch them without gloves on, but I
needed to be able to feel what I was doing with the piece so I didn’t
mangle it under the microscope so they acquiesced to my needs.

Daniel R. Spirer, G.G.
Daniel R. Spirer Jewelers, LLC
1780 Massachusetts Ave.
Cambridge, MA 02140
www.spirerjewelers.com


#9
At the risk of looking ignorant, I'll say that I've never heard of
or encountered a foil-back diamond. 

Benvenuto Cellini wrote (bragged really) about how good he was at
foiling diamonds. If I had not read his autobiography I would not
have bothered to put the electronic diamond tester to it. It tested
OK. It looks like gold paint on the back. My diamond dealer says he
has seen them in India.

The stone broke on the first tool stroke trying to get it out of a
bezel. It is still held together and the customer has descided to
just leave it as it is. I will complete her project using uncut
diamonds, as she wants a sort of primative look to the stones.

Thanks to everyone who offered their help with this.

Stephen Walker


#10
I'll say that I've never heard of or encountered a foil-back
diamond. 

Foil-backed diamonds is the old way of setting of flat backed
diamonds (it is call in Europe ‘Antwerp rose’). This cut was (so I
believe) the norm before the brilliant cut became popular. A curved
bit of fine silver foil reflects the light back through the diamond.
When I was in repairs, this setting was not uncommon (Holland late
70ties). I often had to anneal the work and stone, just to bring back
the oxidised foil to white. The difference was dramatic, as you can
believe. This was the cheapest option. Lifting the stone and
replacing the foil was the more expensive option. We never did
polish back the existing foil. The fine silver foil was rolled hard,
polished with a burnisher and domed to fit. The setting needed to be
tide, to avoid liquid to seep in.

Cheers
Peter Deckers
New Zealand