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Best way to set a cabachon with a rounded back


#1

This is my first time asking a question on this site, so I hope that
I’m doing it right!

I have a couple pear shaped topaz cabachons I would like to set back
to back. I ordered them from a website and when they came I
discovered that rather than flat backs, the backs are slightly
rounded, making it hard to set them as I normally would a cabachon. I
don’t know the best way to deal with this. Do I add an inner wire
seat to my bezel cup? Cut a hole in the bottom of the bezel cup (this
is problematic because they are set back to back)? Any tips would be
appreciated! Thanks so much.

Mackenzie


#2

I would cut the rounded back flat on a lapidary machine. I have the
advantage, that I cut my own stones, so that would be my simple
solution.

John


#3

I have encountered this in setting poorly cut Cabs.

To a sometimes rocky cab, I have soldered silver (or metal I’m using
as my media) into the bezel cup to stop the cab from rocking.

I have heard some cheep work is done with sawdust, or even epoxy.

The wire trick you mentioned sounds to me the best method…

That said I don’t consider myself a professional. What would the
others suggest?

Best regards
Samantha Ann


#4
I discovered that rather than flat backs, the backs are slightly
rounded, making it hard to set them as I normally would a
cabachon. I don't know the best way to deal with this. 

I’d say the best way is to make the backs flat. A quick and easy job
for a flat lap, or even just diamond slurry on a piece of plate
glass.

Al Balmer
Pine City, NY


#5

Hi Mackenzie

To set your pear shaped cabuchons, here’s a trick that deals with the
rounded backs. Measure the height of your cabs, and for example, a
1/8" tall bezel is the right height, I would add another millimeter
to the height of bezel. Make the bezel fit the cabs, and then take
20g. or 18g. round wire, make a wire ring to fit inside the bezel,
and solder it in. Emery the backs of bezels flat, so the round wire
soldered into the bezels become seamless, and you have a nice open
back bezel that lets the round backs sit effectively in bezels. I do
that to all of my odd cabs that have rounded backs. Very effective
for Mabe pearls. It’s also economical, since you save a lot in not
using sheet metal. When I make gold bezels, I make them open-back,
since it is too expensive to use gold sheet, esp, on a large bezel.
Hope that helps. I set hundreds of stones a year, so I’ve had to be
creative in dealing with all of the freeform cabs I encounter.

Joy


#6

Joy - so no sheet metal on the back of the bezel at all? just the
wire and an extra tall bezel wire? Do I understand correctly? Sounds
like an easy solution with the right thickness of wire. The stones I
have are topaz cabs - so therefore pretty transparent, wouldn’t
sanding the bottoms effect the look of the stones from the top?

Mackenzie


#7

Cut the seat to mimic the pavilion or back of the stone it is so
easy and doesn’t require any cutting of the stone.

Russ
The Jewelry CAD Institute


#8

Mackenzie,

The stones I have are topaz cabs - so therefore pretty
transparent, wouldn't sanding the bottoms effect the look of the
stones from the top? 

Yes, sanding the back unless you polish it will be seen and will not
look attractive.

One solution is to make the bezel and make an inner bezel the right
height that fits inside

that holds the cab up so the back does not touch the back plate.
This inside piece does not have to be soldered in.

Once you make the bezel with the back plate and see what the cab
looks like in the bezel

with the back plate you can decide on whether it would look better
without metal behind

the cab. Sometimes the back plate reflects light and washes out the
color.

Another way to do it is to use the bezel flat and use two tweezers to
hold a wire in the right position to solder the wire down the right
distance from the top, then solder the bezel into a circle. When you
use wire, you need to cut a seat for the edge of the cab to rest on
because of the rounded bottom. Ball bur works.

I have used a flat strip of silver bezel, a flat strip of 18kt and
soldered a wire where the two metals meet, soldered them flat and
formed into a bezel to make a tall bezel so I could have a gold
bezel on a sterling piece for a large faceted gem. Large gems, deep
pavilion, all 18kt bezel would have been to expensive for my
customer, stayed in the budget and really set the piece off this way.
I did the soldering of the wire to the flat strips at one time and
the strips were soldered together at the same time.

Richard Hart G.G.
Denver, Co.


#9

I usually find a thin piece of wire with material like the body of
the piece and form it to fit the outer edge of the bezel. That way
the stone can dip in the center and seat on the edge without rocking
in the setting.


#10

you can leave the back if you want it to have a back. Just polish
it. The wire will hold the stone up either way.


#11

Mackenzie-

if you want the stone open on the backside then the wire method other
posters have described works well…it creates the seat ( liked
stepped bezel wire would)… if you don’t need light to come through
the stone and have designed a solid backing to the bezel dry boxwood
sawdust in the bezel to level the stone is a very old tried and true
method - native american silversmiths have done it with turquoise
for centuries…

rer


#12

Mackenzie,

so no sheet metal on the back of the bezel at all? just the wire
and an extra tall bezel wire? Do I understand correctly? Sounds
like an easy solution with the right thickness of wire.  

Nope, sheet metal is not needed for open back bezels. Just go with a
taller bezel, make a wire ring to fit inside of bezel, solder it
inside the bezel at the base, emery flat so that the solder seam
between the bezel and wire disappears, and then the stone look like
they are floating. No backing to interfere with light. Not one piece
of sheet metal is needed as a backplate. I save a lot on the sheet
metal alone. If you want to see some pictures, just email me at
offline and I’ll send you some images of my open back bezels.

Joy


#13

I often bed cabochons set in closed bezels in silicon rubber. Gives a
firm seat when it sets up, gives some shock resistance and easy to
remove stones if later servicing is necessary. Let the silicon set up
before burnishing the bezels over. HOWEVER, if the stones are
transparent I would use the “ring” exactly the size of the stone
inside the bezel as a seat. Transparent stones need to be set so they
may be cleaned. Any closed bezel will still allow some moisture/dirt
to penetrate eventually, and needs to be cleaned. Also, most
transparent stones are cut with a convex bottom to provide a lens
effect, making a bright appearance if properly done. A flat back will
not focus light back up, and give a “window” effect. Incidentally,
star and catseye stones, if very transparent, are usually cut with a
frosted back to accentuate the optical effect.