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Flush setting gemstones


#1

Do you have to drill completely though metal to flush set stones? I
know this is normally what you are supposed to do. I have a number of
designs in mind where a flush setting would look the best and
probably be easier in the long run, but the metal and design would be
too thick and/or shaped in a way that would not allow for a full hole
through the metal. Thanks for your help.


#2

The critical angles that a lapidary uses to facet the gem are based
on an air/gem interface, not a metal/gem interface. Setting the stone
into a metal interface with the gem surfaces will reduce the
brilliance of the light being back our the table due to the internal
reflection/refraction of the rays. Thus, not drilling through the
metal will probably reduce the beauty of the stone.

John


#3

You do not have to drill through the metal. It makes easier to clean
them if you do.


#4

Ginger- ALL stones should be fully drilled out or open behind the
stone.

The only exception is when setting an opaque cab with an ugly back
side.

Micro pave drives me crazy because no one drills out behind the
stones.

You can’t clean them. Old schoolers like Tim and me not only drill
out behind our stones we also hand ajour. It’s the sign of fine
craftsmanship.

Have fun and make lots of jewelry.

Jo Haemer
timothywgreen.com


#5
The critical angles that a lapidary uses to facet the gem are
based on an air/gem interface, not a metal/gem interface. Setting
the stone into a metal interface with the gem surfaces will reduce
the brilliance of the light being back our the table due to the
internal reflection/refraction of the rays. Thus, not drilling
through the metal will probably reduce the beauty of the stone. 

Well, yes, but…

With at least higher Refractive index stones like diamond and a
number of others, the total internal reflection from facet surfaces
that gives stones their brilliance depends, as you say, on the
air/gem interface. Not drilling the metal under the stone does not
change this, and if the stone is clean, you cannot then see the metal
under the stone. Not drilling the metal, if the stone is well sealed
by the flush setting or bezel or pave seat means less dirt can get
to the stone, so it stays clean longer. But dirt and grease being
what they are, eventually they’ll get in there, and the pavilion of
the stone gets dirty, no matter what, and then the beauty of the
stone suffers. But it’s mostly the dirt, not the metal under the
stone, that does this, at least with stones having a high enough R.
I. to totally reflect light back out the table. With lower R. I.
stones, where there is some “read through”, meaning you can see
what’s behind the stone even when the stone is clean, then of course
whatever is behind the stone affects the beauty (thus the practice of
"foiling" gems back in times before modern optics were understood in
facetting. You still occasionally see it with tansparent cabochon
materials…, or similar practices such as darkening/oxidizing the
metal behind, for example, opals, to increase contrast) Then, what
the metal behind the stone looks like becomes a design choice, to
include knowledge of what it will look like when dirty. The biggest
difference, I think, is simply that we pretty much know that no
matter what, the pavillions will get dirty, and brilliance will
suffer. Drilling behind the stones means it’s then easy to clean the
jewelry again, restoring brilliance. With lower R. I stones, drilling
or azuring the metal underneath means you see open space, not
reflective metal, under the stone. Often, this is a better look, but
not always.


#6
The critical angles that a lapidary uses to facet the gem are
based on an air/gem interface, not a metal/gem interface. Setting
the stone into a metal interface with the gem surfaces will reduce
the brilliance of the light being back our the table due to the
internal reflection/refraction of the rays. Thus, not drilling
through the metal will probably reduce the beauty of the stone. 

Not right, if the gem is faceted and the pavilion is cut to the
correct angle for the critical angle for the R. I. of that particular
gem, unless the metal is touching the pavilion, the critical angle
does not change.

What can change the critical angle is anything that binds dirt to
the pavilion and that will change the critical angle.

Flush set diamonds, without the hole drilled completely through the
metal will allow dirt and oil to work its way down and it cannot be
cleaned, the dirt will carbonize and that will make the diamond look
dark or black.

If a gem is not cut properly, how it is set Makes no difference.

Richard Hart, G. G.


#7

Good explanation, Peter. I’d only add that even low RI stones can be
cut so as to not window, though they may turn out deep enough that
setting is a problem. Also, it is perfectly possible (and
unfortunately, not uncommon) to cut even high RI stones with a
window.

Al Balmer


#8
Micro pave drives me crazy because no one drills out behind the
stones. 

A couple thoughts, Jo.

With the way most micro-pave is done, the stones are not sitting
firmly in a seat that goes all the way around the girdle. The metal
is shaped before the stones are set, with a partial (or full) drill
hole underneath, opened up usually with a ball bur so the stone sits
snug at the right depth. But then there is a lengthwise groove cut,
and crosswise grooves cut at each hole, to shape the remaining metal
into prongs. The result is that the stones contact the metal at each
prong, but in between, the girdles are still above the metal,
creating a slight gap to the space drilled out underneath. This is
more than enough access to the pavilions of the stones to allow
effective cleaning with ultrasonics and steam cleaners. The need to
drill through in order to clean the backs is not quite the same with
micropave work, as it would be with traditional pave.

Second, with micropave, the usually very small size of the stones
and attendant drill holes substantially increases the problem with
breaking drill bits, since often the ration of drill size to the
depth of the hole is a large one. Broken drill bits are a PIA, and
even with skill, those usually very small drills do end up breaking
enough to slow you down, and thus raise costs. Given that it’s not
really necessary for cleaning (the main reason to drill through) why
saddle yourself (as a setter) with the added time and trouble when
the only real reason is the simple inertia of tradition?

Also, given the small sizes of the drill holes and often, thicker
metal, it’s common when hand drilling, for the backsides of the holes
to not be quite a well lined up as on top. yeah, that’s skill, and it
varies from setter to setter, but still, when the insides of the
drill holes end up being unevenly spaced, or when you end up having
to try and even up the appearance by burring out the insides of the
holes more than just a small chamfer, then I’m not sure the
appearance is improved any. What can be affected though, is the
overall structural integrity of the piece. Unlike traditional pave
work, where a major factor in stone security is the friction fit of
the stones in their seats all the way around, with micro pave the
contact between metal and stones is mostly at those tiny prongs. That
means that the stones are more prone to loosening in the event the
ring (or other piece) is bent. Lots of drill holes simply makes the
metal weaker, and more able to be bent. It’s a small consideration,
perhaps, but still there. Not drilling all the way through leaves the
metal slightly stronger. For some of the most delicate designs, this
can be a significant difference in durability…

Just my two cents, playing devils advocate here… :slight_smile:

Peter Rowe


#9
Flush set diamonds, without the hole drilled completely through
the metal will allow dirt and oil to work its way down and it
cannot be cleaned, the dirt will carbonize and that will make the
diamond look dark or black. 

I’m guessing then that setting gemstones via casting would cause
similar issues as well?


#10
Flush set diamonds, without the hole drilled completely through the
metal will allow dirt and oil to work its way down and it cannot be
cleaned, the dirt will carbonize and that will make the diamond
look dark or black. 
I'm guessing then that setting gemstones via casting would cause
similar issues as well? 

First, a comment on the prior posting, quoted above. The dirt will
not automatically carbonize. To do that, you have to heat it to a
high enough temperature to burn it. That will happen if you heat it
with a torch, such as in repair work. Normally, a principal practice
in repair work is to be sure the diamonds are clean, and then coated
properly with a protective coating, usually boric acid/alcohol. That
protects the stones from oxygen and burning. With a closed back
setting, the boric acid doesn’t reach the back of the stone, so the
stones can burn (they turn milky white) if overheated. Note,
“overheated”. Some heat can be tolerated, even so, if the stones are
clean. But again, with closed back settings, if the dirt, oils,
grease, wax, etc, has made it to the pavilions of the stones, then if
you heat it, you won’t have been able to clean it, and THEN that dirt
will carbonize, and along with it, often also start to burn the
diamonds. But all that does take heat.

To your question, Ginger, casting stones in place specifically
requires that the settings be drilled through, because the casting
investment has to be able to clamp the stones in position in the mold
after the wax is burned out. If the holes are not drilled through,
there will be no support under the stones, and they’ll drop out of
place, and end up imbedded somewhere in your metal, or not attached
at all and floating free in the investment somewhere else than set
in the metal. Not the desired result at all. As with repair work,
stones being cast in place need to be clean, and protected from
burning, usually done with careful control of temperature so the
stones never get quite hot enough during burnout and casting to cause
them to burn. Doing that requires very precise temperature controls,
and very precise wax model development.


#11

In regard to the casting method, I was thinking of delft clay instead
of lost wax when I asked this. I saw in a gemstone setting book that
one person was making a pendant and just laid the stones where they
wanted them to be before closing and pouring in the metal.


#12
In regard to the casting method, I was thinking of delft clay
instead of lost wax when I asked this. I saw in a gemstone setting
book that one person was making a pendant and just laid the stones
where they wanted them to be before closing and pouring in the
metal. 

While the procedure to cast stones in place with Delft clay may
differ from doing it in wax with conventional investment casting, the
requirment that the stone be actually held in place by the mold
material (in this case, Delft clay), remains the same.

To illustrate, if your intended casting is a simple ingot shape, and
you wish a stone set in it so it’s flush with the surface but
showing, and you simply press the crown of the stone into the clay in
the right position, if it stayed there during metal pouring, then
perhaps you’d get what you wish, though the metal would be in total
contact with the pavilion of the stone. But even with that
undesireable result (too much heat for even diamonds, and the optics
would be all wrong for an attractive stone), it isn’t what you’d get.
The metal is much denser than any stone, so when the liquid metal
gets to that part of the mold, the stone would behave just like a
cork in water, and try to float up into the metal.

If you somehow adhered the stone in place (glued to the clay?), then
perhaps that might not happen, but even so, the result, without any
air space behind the stone, would look off, maybe even just plain
terrible.

To fix this, your original mold in the Delft clay would include the
stone in the model, and the model would have an open cavity behind
the stone, extending out the back of the model. With the model
removed from the clay, you’d then have the impression of the stone on
the front part of the mold, and on the back, a column of clay leading
up to the pavilion of the stone. Place the stone in one half of the
mold, close it up carefully, and now, in the mold, the stone has
clay in front of it, so the front stay’s clear of metal (except,
hopefully, some metal that comes around the girdle to hold it, either
like a bezel or like prongs, etc). And there will be this column of
clay holding the stone from the back too, keeping the metal away from
the pavilion as well as holding the stone in position. If the total
area of the stone that’s actually exposed to the metal is kept at a
minimum, just enough to hold it securely, and the overall mass of
the casting is kept fairly light, so the casting cools before the
stone has too much chance of getting too hot for it’s survival, then
this could work.

There is still the issue of heat shock. In conventional
stone-in-place casting, the stone is in the mold during burnout, and
it’s been heated slowly to that temp and then cooled slowly to the
mold’s casting temp. So the stone is hot, but not destructivly so, at
the point when the molten metal hits it. This still presents a heat
shock, but some stones, like diamond, can withstand this heat shock,
especially rapid heating (rapid cooling can be worse). But there are
limits.

With Delft clay, the stone would be at your room temperature when
the molten metal hits it. That’s a much greater temperature
differential for the stone to survive. It may, but it’s riskier.

Coupled with the fact that delft clay would tend to lack the degree
of control you have over just how much or little the contact area of
the molten metal to the stone is, with the clay tending to more
contact, then the issue of accidentally overheating the stone and
cracking or burning it when molten metal hits it becomes much more
serious.

But the flip side is that in the clay, the stone does not have to
withstand extended heating for burnout. Just the brief but intense
shock of the molten metal hitting it, while starting out relatively
cool, and insulated where not touched by metal by the initially cool
clay. So who knows. Some stones that don’t work for conventional cast
in place setting might work with Delft, while stones that work with
Delft might not work with conventional materials.

Back when commercial casters were first figuring out how to cast
diamonds in place, they were making things with excessivly light
metal designs to minimize contact and shock. The jewelry was so
delicate it was flimsy, and even the slightest deformation would tend
to loosen and release diamonds. Rings from back then were almost
impossible to size without loosening stones, and then tightening them
was a nightmare or impossible. But more experience, different
burnout procedures, tight controls, and investment formulas optimized
for stone in place casting have led to much higher sucess ratios,
with the best of such work being sometimes difficult to distinguish
as being cast in place instead of conventionally set. (Even so, there
are still the occasional stones that don’t survive the process.) But
it took a lot of work and trial and error to get that conventional
material cast in place process to the state that it is today. I’d
expect that trying this with Delft clay would be much less likely to
give you sucess, at least on any sort of regular basis.

But don’t just take my opinion for this. Experiment. History is rife
with cases of experts telling amateurs exactly why such and such an
idea was nuts and would never work, meanwhile the amateurs, perhaps
not hearing or believing that they were nuts and their ideas would
never work, went ahead and found ways to make it work. If humans
always heeded the experts, and never took chances on the unknown, we
might never have even made it to the stone age, much less beyond it.
And besides. As someone who’s reasonably capable at conventional
stone setting metals, and equipped to do so, my incentive for
embracing stone in place casting is slim and whether my scepticism is
justified or bias or just plain bein’ uppity about it all. Who knows.
Try it and see. I suggest initial experiments be done without the
need for initial sucess, and with inexpensive materials till you’re
sure it works

Peter Rowe


#13

Thank you for everyone’s thoughts and help.