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Centrifugal casting with diamonds in place


#1

I have a baguette diamond ring to channel set and the baguettes are
of course all different sizes (typical eh) a way around this would be
to make a wax blank and cast with the diamonds in place but the only
time i have attempted to cast with diamonds they seemed burnt (ie
turned dull ) is there a trick to casting with diamonds??


#2

Hi,

Please make sure your furnace burnout does not exceed 630 degrees and
you may want to add 0.5-1% of boric acid into your investment powder
to prevent your diamond been “burnt” (i.e. 1kg of investment powder
5-10g of boric acid)You will experience “hard” investment powder
after casting so you have some cleaning to do. Make sure you mix well
with the powder

Good luck
stepfan chong


#3
cast with the diamonds in place but the only time i have attempted
to cast with diamonds they seemed burnt 

John, I’ve never actually done it - hopefully someone who has will
post. I was thinking about it once, and did some research, though.
First, there are investments that contain flux, or you can mix it in

  • you need that. More importantly is that you MUST steam dewax. The
    combination of the high heat needed for burnout and the carbon from
    the wax is the very thing that burns the diamonds. If you steam
    dewax, all you need to do is warm the flask to casting temp. I
    forget where there was good info, but it seems like it was either
    Gesswein or I. Shor that had a whole article about it. The old
    long-defunct Nova Stylings had a beautiful line of cast-in-place
    baguette jewelry… Ah the good old days.

http://www.donivanandmaggiora.com


#4

Yes, very tricky! You have to use special investment and long low
slow burnout, then you have to dig the pice out of the investment. DO
NOT QUENCH! Let cool by itself. Also you may try steaming your flask
first to Pre- melt the wax in the flask.


#5

I have cast diamonds in place several times. The trick is to either
use a stone in place investment or add 10% boric acid to the
investment mix. The burnout should never exceed 1050 F. and should
be held at that temp for at least twice the number of hours you would
hold at 1350 on a normal basis. The burnout of course depends on the
size and number of flasks in the oven. Ron Amos with Hi-Tech
Precious Metals and Refining ramos@hitechpmr.com did an extensive
study of stone in place casting a few years ago. He was very helpful
when we first started doing it here at TIJT.

Shannon Calloway


#6

There are articles about stones-in-place casting on the web, which a
thorough Google search should find, although I’m not sure how
suitable they are for centrifugal casting:

http://www.srs-ltd.co.uk/clickset/General/index.htm
http://www.colored-stone.com/stories/sep02/designs2.cfm
http://www.shorinternational.com/CastStoneInWax.htm
http://www.srs-ltd.co.uk/technical/stone_place_casting.html

I’m sure there are many more, but the links above seem to give lots
of

Helen
UK


#7

I am not a jeweler, so pardon me while I dazzle you all with my
ignorance. I know that some people do this, as the practice was
discussed in some depth in another thread some months ago. Still, it
seems to me that casting with any stones in place would qualify as a
Really Bad Idea for several reasons.

First, to burn out the mold, you heat it to, what, around 1000C or
so? Then you pour melted gold into the cavity, also around that
temperature. Then it takes a bit for the whole thing to cool enough
to handle, so you have a heat soaking period.

Most colored stones are heat treated at temperatures ranging from
400C to 1300C, depending on the stone and the effect desired. Many
colored stones are sensitive to changes in temperature, so what you
would break out of the mold at the end of the process would be either
more or less heat treated gems preset in a raw casting, or a casting
with shattered pieces of gemstone attached to it. For ethical
reasons, you would need to disclose the heat treatment. With
diamonds, I can’t remember offhand if heating is a standard
treatment, or even an effective one. In any case you would have a
diamond in a piece that still needs to be cleaned and polished
somehow. It seems to me that it would be very difficult to cast a
decent setting, clean it up, and polish it with the stone in place.

Going back to the heat thing, remember that diamond is really just
crystallized carbon. They last a long time, but they are definitely
NOT forever, at least in an oxidizing atmosphere. At the surface of a
diamond, the crystal lattice is slowly but continually breaking up,
leaving a film of carbon dust that can become perceptible in only a
few hundred years. (Did I mention that this process is slow?) By
toasting a diamond at kiln temperatures, you risk speeding this
process up a lot, thereby ruining the polish on the gem, at the very
least. According to Wikipedia, diamond can be burned at temperatures
above 800C.

If you try to avoid this by burning out and preheating your mold to,
say, 700C, then pouring in your molten gold, you run a huge risk of
thermal shock to the diamond, and a lesser but still real risk to
the mold itself. Once again, thermal shock can do horrible things to
any gemstone, even one as tough as diamond.

Finally, even if you don’t ruin the gem with heat, how are you going
to file and polish the setting without scratching the diamond? The
whole thing just seems like more work and risk than it is worth.

For what it’s worth,

Steve McQueen
gemsevermore.com


#8
I am not a jeweler, so pardon me while I dazzle you all with my
ignorance. I know that some people do this, as the practice was
discussed in some depth in another thread some months ago. Still,
it seems to me that casting with any stones in place would qualify
as a Really Bad Idea for several reasons. 

Casting in place is the worst idea that I have ever encountered. <>
From jewelers point of view: Stone setting is the finest part of the
process of creating a jewel. It is the stage where work of all
previously engaged jewelers is either enhanced and brought to
fruition, or totally ruined. Stone setters were always occupying
special place in jewelers shop. To substitute this for someone
sticking diamonds in wax and casting diamonds in place is the insult
to any practicing jeweler. Item (i intentionally do not use term
"jewelry") produces this way are inferior in all the aspects and
should be avoided at any cost.

Leonid Surpin
www.studioarete.com


#9

A lot of info from a non jeweler! lol. The Indians have been using
this technology on a large scale for the last 10 years that I know
of. Successfully I might add. I see, understand, and agree with
everything you’re saying about heat treatments, thermal shock, etc.
The cast in place process is usually used on diamonds and cz’s. The
heat treatments that you want to disclose are used on colored stones
(Sapphire esp) not diamonds – at least not I-J-K I1-2 1-2 and 3
pointers. Put aside HPHT for a second. The process done right
(controlled burnout and casting temps) save a LOT of stone setting
labor. I don’t see any problem with it, when it is used in the
context for which it was intended. $99-199 cluster rings and so on.
You wouldn’t cast in place a bunch of G/VS 15 pointers. I wouldn’t…

Stanley Bright
Owner
A&M Jewelers
Baltimore, MD


#10
Still, it seems to me that casting with any stones in place would
qualify as a Really Bad Idea for several reasons. 

Well it can be a bad day in the shop for many of the reasons you
mention. That being said it is in use by mostly industrial jewelry
production companies on lower end merchandise. It requires extremely
good process control and a lot of engineering to get it right. The
seats must be cut properly in the waxes, the stones sorted and graded
for likely candidates, burnout and casting parameters must be
followed precisely. Even then there is a fair probability of loss of
some stones to flaws that could not handle the rigors of the
process. I would never use stone in place casting on a customers
stones. The risk is too high, especially if one has no experience in
the process.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#11
Casting in place is the worst idea that I have ever encountered.
From jewelers point of view: 

Leonid, I fully agree with you on this. The first generation of
goods made this way were truly horrendous. The nature of casting
diamonds in place is such that it’s important to minimize the contact
between metal and diamond, and there must be enough space open under
the stones so the investment can securely hold the stones in position
during burnout and casting. What that results in is settings with
thin webs of metal holding the two sides of a channel together, or
otherwise reducing the amount of metal supporting the stones and
holding the setting together to a bare minimum. Many of those early
generation cast in place rings were so fragile that there was no way
to even size the ring without stones falling out all over the place,
and then, too fragile a mounting to allow resetting or often even any
sort of repair or rebuild short of totally remaking the ring.

With that said, though, the Indian and Chinese manufacturers have
gotten a LOT better at this. I’ve seen some cast in place pieces
where only very careful examination of the settings revealed the
method, and which, at least as far as I could tell, were sturdy
enough and well enough engineered to hold up well. I know several
chain store operations where a large percentage of the merchandise is
made this way, and it’s not so bad mechanically or even
aesthetically, at least for mass produced pieces. It’s not, of
course, comparable to high end hand made work, or even commercial
work with fine hand setting, but it doesn’t really try to be, selling
at lower price points.

If the end result of cast in place technology results in pieces that
are indeed decent enough quality to meet the normal expectations of
consumers and bench workers who may need to work on the things, then
I think there is a place for the stuff. Setters and fine jewelers
might, as you do, consider it an affront to traditions and
craftsmanship, and I don’t disagree. But fighting it too hard is
tilting at proverbial windmills. Marketing considerations mean that
the stuff is likely here to stay, and we’d all be best off not
bothering with wailing about it, but instead considering it a
challenge to our creativity and skill, to produce jewelry that cannot
be made well this way, with which we can compete. If the mass
overseas marketers and manufacturers wish to take over the low end
market, I say let em. We likely can’t stop them. Instead of trying,
we can make sure that our real stock in trade, the finest level of
work, remains good enough, and desireable enough, that there will
remain a market for our skilled production that the mass manufactured
stuff cannot threaten.

but of course this still doesn’t address the problem of how to deal
with that portion of the cast in place merchandise that shouldn’t
exist. My main beef here is the invisible set crap. This type of
setting is quite hard to do really well, but not so hard to do
marginally enough so it will go out the door. So we see the nice look
of invisible setting seducing manufacturers to crank out cheaply done
hand set invisible setting work, and of course, the cast in place
crowd has figured out they can almost equal the quality of the poor
quality invisible set work out there. So we’ve got a bunch of
invisible set merchandise out there made either with stones cast in
place, or quickly hand set, that’s junk. The public likes the look,
but we jewelers are stuck with then having to work with the stuff.
Rings that cannot be sized, stones that, once loose, can only be
tightened with super glue or some other desperate temporary patch
job hacking. And the worst? Retailers who, even whey they know the
stuff is crap, still insist on carrying it because they can buy it
cheap. And when they bring the stuff to us to size, and we tell them
it might fall apart, even then they don’t care all that much.

And not only does that sort of junk hurt the public perception of
jewelers in general, since they cannot distinguish between retailers
who have enough professional pride to avoid the crap and those who
don’t, but it makes we goldsmiths called upon to try and rescue these
pieces of junk, look incompetent when we tell consumers that the
stuff can’t be properly fixed, even if they only just bought it. All
for the sake of satisfying an unreasonable fashion demand, the folks
who foist this junk off on people end up hurting the whole field.
And that makes me as annoyed as stone in place casting seems to have
made you.

It’s too bad, really. There IS a place in the field for this method
of setting. I’ve seen some pieces made this way that could not have
been made any other way. Such geometries, where the design pretty
much prevents normal setting techniques, but which can successfully
make a good piece of jewelry by casting the stone(s) in place, is a
worthwhile addition to the arsenal of technology we can all use. It’s
too bad that the apparent economic advantages of reducing setting
labor costs ends up seducing the manufacturers and designers into
making junk as well.

cheers
Peter Rowe


#12

Leonid,

For what it is worth, for once I agree with you re casting stones in
place. Roger


#13
It's too bad, really. There IS a place in the field for this
method of setting. I've seen some pieces made this way that could
not have been made any other way. 

Actually it is worse. I had a conversation recently with a client. He
was telling me of one jeweler who actually telling to his customers
that he sets stones with crazy glue and that is why they do not have
to worry that stones would fell out. I rest my case.

Leonid Surpin
www.studioarete.com


#14

What worries me about the process is how the stones stay in place
once the wax has been burned out. Isn’t there a danger of the stones
falling into the void? I’m struggling to get my head round it. I
suppose anything that will be eventually occupied by air in a
design, will be occupied by investment whilst in the casting process,
so is that what holds the stones in place after wax removal?

Helen
UK


#15

Hi Helen:

You have to expose the back or sides of the stone somehow. Normally,
(on a ring) you just open out the back of the setting, and the open
back forms a pillar of investment to hold the rock in place once the
wax’s gone. You have to have some way to retain it into the
investment once the wax is gone, but the range of ways to get there
is pretty broad. Grabbing the sides works reasonably well too, you
just have to watch out for the direction of the metal flow as the
pattern fills. (you really want to rig the flow to be inline with the
grabbing areas.) All you have to remember is that the empty void of
’not wax’ becomes the holding mechanism. Once you learn to think
inside out like that, it’s easy.

I do basic ‘rock in wax’ casting with my beginners, with pretty good
success. (using lab rubies or CZ’s).

Regards,
Brian Meek.


#16
What worries me about the process is how the stones stay in place
once the wax has been burned out. Isn't there a danger of the
stones falling into the void? I'm struggling to get my head round
it. I suppose anything that will be eventually occupied by air in a
design, will be occupied by investment whilst in the casting
process, so is that what holds the stones in place after wax
removal? 

Stones falling out of place during burnout or casting is maybe the
biggest problem with stone in place casting. If the seats are not
designed to allow the investment to grip the stone sufficiently then
they will definitely fall out of place.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550