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Restoring finish to opal


#1

Customer brought in a silver ring, the opal looks like it’s just
been worn enough to take the polish off the surface. (It’s a very
favorite ring) The the fire is barely visible below the cloudy
surface. Is there anything I can do about this? I’m basically a bench
jeweler/metalsmith, no lapidary experience at all. I had thought I
could restore it using opticon, but that seemed like a less than
desirable solution. Do I need to find a stone cutter to polish the
surface again? It’s bezel set in a sterling ring and looks to be a
very pretty stone if it was shiny again.

Thanks!
Barb Baur


#2

Hi Barb I’ve used a product called Linde A Powder and it works
beautifully on opal, animal teeth and ivory (no, I do not use
ivory). Unfortunately I don’t know where to tell you to get it.

Margie Mersky
http://www.mmwaxmodels.com


#3

Is it an opal dublet or triplet? and is it boulder opal or precious?
I had this challenge a few months back - these details matter. Could
be a simple solution like having a lapidary heat off the quartz top
and re-apply the optical adhesive which may have started to separate

  • causing that ‘cloudy’ appearance (I say simple but in fact it’s a
    bit tricky).

<> sadly the opal may have been re-saturated with ‘liquids’ over
the years (some older ladies like to do dishes with their opal rings
on cringe) there is no solution for this problem.

Cheers,
Taylor in Toronto


#4

Hi Barb,

Here’s what I do in such a situation. It is a common one. Usually
the wear is concentrated on the top of the stone, which is the most
exposed part. That also means that it is the part you are most
likely to be able to get it with a sanding stick. I gently go over
the stone with a 1,200 grit silicon carbide wet-or-dry sanding
stick, maybe glued down to a popsicle stick or medical tongue
depresser. Sand, gently, with lots of water, until the reachable
parts of the stone are brought to a fine even silky frostedness.

Usually wear pitting like you describe doesn’t require anything
coarser than 1,200 grit to remove. From that silky 1,200 grit
sanding finish you can proceed directly to re-polish the stone. Do
this with a small leather wheel in the Foredom, at fairly slow
speed, kept wet (don’t let it get dry - that risks heat build up
which may crack the stone), applying a slurry of any of the usual
polishing compounds such as cerium oxide, tin oxide or aluminum
oxide. Move the wheel around over the stone, don’t let it dwell in
one place. You could use a felt wheel too but felt builds up heat
quickly which could be risky.

If you’re not confident using the Foredom, you can do the polishing
by hand also by glueing a leather strip to a wooden ruler or similar
and applying the polishing compound to the stick. Again, do it wet.
Use a light touch and frequently check to see what’s happening.

Hope that helps

Hans Durstling
Moncton, Canada


#5

Hi there, It sounds like now you will have to seek out a cutter…It
is our understanding that opticon is a form of glue…It needs to
come off the surface and then the opal can be repolished…Take care,
John

Donivan


#6

Barb,

Opal is one of the easiest gems to restore a polish to. First make
sure it is a solid Opal and not a triplet with a Quartz top. If it
is a solid opal simply wet sand it lightly with very fine Waterproof
Silicon Carbide Sandpaper. Try starting with 1500 grit. Make sure you
keep the Opal wet. After lightly sanding it rinse and dry it to check
the surface. If the scratches are too deep for this fine paper drop
down in grit and ten work back up to the 1500. Sand in different
directions. Once you have the scratches removed take a new and clean
cotton wheel and place in your Flexshaft. Charge the wheel with
Cerium Oxide mixed with water to Polish the surface of the stone.
Keep the stone wet and the Cerium Oxide should be mixed so as not to
be pasty.

Good Luck
Greg DeMark
email: greg@demarkjewelry.com
Website: www.demarkjewelry.com
Website: www.outdrs.net/~demark


#7

Yes, Barb, it needs to be repolished, by someone who knows about
cutting and polishing opal. Opal is soft, and scratches easily. It is
also brittle, and for these reasons not too often used in rings, at
least not bezel-set. No opticon! And then you might consider setting
it a bit differently, so the opal is a little more protected.

Margaret


#8

It is definitely possible to polish the surface of a bezel set opal
WITHOUT removing it from the ring. I regularly use Harry Kazanjian
and Sons in L.A. (One of the best cutters and polishers that I know.)
213-624-4131 ask for Cookie or Virginia.

David Barzilay
Lord of the Rings
607 S Hill St Ste 850
Los Angeles, CA 90014-1718
213-488-9157


#9

Yup, you’d have to have it polished again; the stone wouldn’t
necessarily have to be removed from the setting. Opal’s soft so it
could be done easily and quickly.


#10

What Taylor says about a possible separating doublet or triplet is a
possibility, but it sounded from the first post more like this is a
solid opal that has simply lost its polish. The standard for
polishing opals is either 50 or 100K diamond on a poly pad or cerium
oxide on felt. I prefer the latter myself. Linde A is not necessary.
Also, opals do not ‘re-saturate’. Once the internal fluids have
dissapated, they will not take on moisture again. When ladies wear
their opals for doing dishes, they sometimes turn slightly to a
yellowish color on the surface but the internal structure remains
the same.

It is important to keep a good polish on opal as that produces a
glassy surface and reduces the possibility of ‘crazing’ and best
displays the internal ‘fire’. In reality, virtually all opals will
craze or crack in time…some will do it early, others take years.

Because they are relatively soft, 5.5 to 6.5 on Mohs scale though
most around 5.5 to 6, opals will lose their polish fairly easily in
normal wear, especially if not protected. They are reasonably easy
to polish but this is often complicated when they remain in a
setting because it is impossible to get access to the entire
surface. Unless they are flush inlay, the best thing is to take the
stone out of the piece, smooth the entire surface on at least a 600
soft diamond wheel (such as Nova), prepolish on 1200 soft diamond
wheel and then polish on a felt pad with damp cerium oxide turning
at about 200RPM.

Be careful not to chip the stone with taking it out or resetting.
Opal is not only soft but very brittle.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut2


#11

Actually, Opticon is a resin that is commonly used to fill small
cracks or porous stones. It is not useful to ‘resurface’ a stone
unless it can actually permiate the surface.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine Jewelry! @coralnut2


#12
Opal's soft so it could be done easily and quickly. 

Opal can be as hard as 6 1/2 on the Moh’s scale, nearly as hard as
quartz, at 7 on the same scale. So, while not as hard as most gem
materials, it isn’t exactly soft, either. The real problem with opal
is toughness, another element of gemstone durability. It is prone to
breaking and chipping, especially on the edges. It can also craze or
crack for several reasons, not the least of which is heating while
polishing. People have thought of opal as a soft stone for too long,
a lack of toughness is why setting opal in rings and bracelets is
unadvisable. But at least it isn’t as soft as soapstone or
serpentine.

As for polishing out the scratches, most of what’s been posted
already is good advice. If it’s a solid opal, you can easily polish
it in place, either with silicon carbide sticks, or by charging
small cup brushes with diamond compound and working down to finer
grits. If (or when) the scratches are small enough for final
polishing, there are many options. Some recommend cerium or tin
oxides on felt, some recommend the same on leather. Either can be
done with your rotary tool Foredom). Others have their own “secret
recipe.” One of the best opal polishers in SoFl (incidentally, his
name is Dr. Huffman) tells me he uses his own blend of Linde A and
tin oxide on leather. My best polish on opal has always been Holy
Cow on felt.

If you’re not comfortable with the process, contact a lapidary. A
read-through of a mineralogical or gemological book or text can help
you understand the differences between hardness and toughness, as
well as those qualities as applied to gem materials such as opal,
jade serpentine and talc, and the best ways to polish them safely
and well.

James in SoFl


#13

hello barb

There are many factors to consider when repolishing an opal. Is the
stone a natural opal or is the stone a synthetic opal (there is a
lot of synthetic opal set in sterling silver out on the market
today). some of this synthetic opal has a polymer impregnated into
it and makes it quite soft (mohs 4.5) and must be treated carefully.
If the stone Is natural there could be internal cracks that can be
hidden by the scratched surface. doublets and triplets can sometimes
have their own problems with delamination of the assembled layers
causing a fogginess in the stone.

It’s best to have a professional lapidary look at the stone to
determine the condition and advise before polishing. Remember, It’s
your customers favorite ring. typical charges to polish an opal in a
setting runs about $20 to $25 dollars. Is it really worth it to try
it yourself and ruin the stone.

Stan McCall
Custom Creative Gem Cutting
http//home.earthlink.net/~custom-creative/


#14

Barb, Check out your local rock shop, of one of the mail-order or
online suppliers of rockhounds’ products. (However; you will need to
have the right cutting and polishing equipment in order to use it.

Margaret


#15
opals do not 're-saturate'.  Once the internal fluids have
dissapated, they will not take on moisture again.  When ladies
wear their opals for doing dishes, they sometimes turn slightly to
a yellowish color on the surface  but the internal structure
remains the same.

Thanks for the Don, I had always believed (was taught)
Opals were starved for water and would take on additional moisture
until the arranged silicon structure was saturated causing the milky
or faded effect - even complete loss of fire. This is an interesting
topic; it looks like I have some research to do.

Cheers,
Taylor in Toronto


#16
      In reality, virtually all opals will craze or crack in
time....some will do it early, others take years. 

I have opals I cut 20 years ago, I still have them, they are not
cracked and not crazed. Lalique made pieces with opal, I believe in
the late 1800’s, I saw them at L.A. county museum. They were not
cracked, not crazed. I have about a pound of opal I have had for 20
years, uncut. Very few pieces have crazed. The most unstabile is
Mexican jelly opal or Virgin Valley, Idaho.

In my experience, most opals are cracked by the wearer smacking it
against something and shattering it. I believe that it is a myth
that opals dry out. I live in Denver, low humidity, very dry
dehydrating environment, and we have had very good success at
carrying opal at our retail store for over 10 years. A few doublets
have seperated, and a few have spontaniously combusted.(kidding)

Over time, some opals can craze, compared to how many I have, the
number that did craze would not be a deterant for me to not work
with them. I have paid $5,000 an ounce for some material,so I would
be very unhappy if my investment disintegrated over time. What I
have has gone up in value as some opal mining areas are not as
productive now as they once were.

I am not discrediting your experience, it just that my experience
seems to have been different. While cutting opals I have never
ruined the color by overheating, or cracked one during cutting or
polishing. I have gone through color layers, and lost value by
grinding away too much, and I have oriented opal wrong so the best
color was visible only at a significantly tilted angle.

Repolishing opal usually involves resanding as wearing causes
scratches and pitting. Polishing usually does not help unless the
scratches and pits are removed.

Richard in Denver


#17

As word of caution that has not yet been mentioned on polishing opal
I’ve cut thousands of them and teach opal cutting. Before you go any
further you need to find out about the age of the opal. If the
customer has had this ring for a long time or it’s an heirloom,
polishing it could be rather dangerous. Opal can get unstable when
it’s been cut for more than about 20 years. It will not generally
crack spontaneously, but polishing it will change the tensions in the
stone and it might bring on crazing. Trust me, you don’t want to be
responsible for replacing a stone because it’s extremely difficult to
match and can be quite expensive.

I’d first find out how old this ring is and if it’s old at all
decline the operation unless the customer understands the risks. In
that case make sure whatever you do you do let this stone heat up at
all. Again if it’s been cut for even over 10 years the stability with
polishing could be suspect.

Derek Levin


#18
  I'd first find out how old this ring is and if it's old at all
decline the operation unless the customer understands the risks. 

I would go the author of this post one better and say that you would
be wise to apprise the customer of the risk of crazing regardless of
the stone’s age. I have seen opals crack and craze with no human
intervention whatsoever. Repolishing can only increase the risk.

Lee Einer
Dos Manos Jewelry
http://www.dosmanosjewelry.com


#19

Derek,

I respect your experience as an opal cutter but I must confess that
your statements are confusing. I am a Gemologist and I have 32 years
experience as a goldsmith. One of my specialties is the restoration
of Antique and Vintage jewelry. Over the years I have had to
repolish untold numbers of Opals in Antique rings.

The fact is that once an opal is stable it remains stable unless it
has been exposed to extreme heat and cold. If the Opal is kept cool
with water while polishing there should be no damage from crazing
unless that crazing already exists below the surface.

Greg DeMark
greg@demarkjewelry.com
www.demarkjewelry.com
www.outdrs.net/~demark


#20

On a slightly different topic: I have heard that it is possible to
"hide" crazing fractures in an opal. Does anyone know about this?

Douglas Zaruba
35 N. Market St.
Frederick, MD 21701
301 695-1107
@Douglas_Zaruba