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Stone in place casting


#1

I have been running some trials using stone in place casting
with good success - diamonds, CZ’s, genuine and synthetic stones.
Has anyone ever done any research or run across any technical
papers or have first hand experience concerning the integrity of
the stones after they have been through the casting process ? In
other words, if the stone makes it through the casting process,
has it been changed or altered in any way which would effect its
durability out in the field, or its physical make-up which would
be a detriment to the end buyer, or its ability to withstand
daily wear and tear ? Or, is it mainly assumed that if it can
make it through the casting process, then that’s about as abusive
a situation you can get ? Also, some technical papers I have run
across say to put boric acid in your investment to protect the
stones. Does anyone know the purpose of the boric acid and if it
is necessary ?


#2

Hi Bill, I’m not sure of the long term effect of the heat from
the burnout/casting process. I would imagine that it wouldn’t
have any effect on the stones provided they came out from the
process in the same manner as they went in. After all stones are
subjected to extreme heat and pressures during the crystalization
process in mother nature and in the lab and from retipping, etc.
As far as the boric acid goes, it is much like protecting stones
during the soldering process. It coats a protective barrier over
the stones to prevent oxygen from burning or oxidizing them. I
have had good success casting in place and always use boric acid
in the investment. The only drawback is the investment is very
hard to break out of the flask after cooling. Ken Sanders


#3
   Has anyone ever done any research or run across any
technical papers or have first hand experience concerning the
integrity of the stones after they have been through the
casting process ? 

Bill, I have not heard of any such research. I have heard many
papers at the Sante Fe Symposium about casting with stones and I
recall no mention of problems. I have been casting stones in
place for a couple of years and have noticed no decrease in
durability or other problems. the fact that so many major
manufacturers are using this process suggests that it is not a
concern. Many stones are heated to the same temperatures during
some repair procees, without any problems.

 Also, some technical papers I have run across say to put boric
acid in your investment to protect the stones.  Does anyone
know the purpose of the boric acid and if it is necessary ? 

I use boric acid in my investment and cast using a normal
burnout cycle. the boric acid coats the stones just like fire
coat does when soldering. I believe it keeps oxygen from
reaching the surface of the stone and not allowing it to
oxidize. I can’t tell you exactly or technicly why but I know
it works. It is very important that the stones be impecibly
clean to keep them from being scorched.

I am teaching a class at Revere this summer on casting with
stones in place and we will actually be doing several castings
with different shapes and types of stones and injecting a wax
mold around stones. Any one interested can contact the Revere
Academy for specific dates at:

Revere Academy of Jewelry Arts
760 Market Street, Suite 900, San Francisco, CA 94102
phone: (415) 391-4179   fax: (415) 391-7570
e-mail: christine@revereacademy.com

#4

Hello, My name is Arthur Skuratowicz, and I just gave a
presentation about gemology at Santa Fe Symposium this year (the
paper will bepublished in 2000). And a topic I am researching
for next years Symposium deals with the effects of casting has
on stones cast in place. I hope the results can be useful.

Later,

Arthur Skuratowicz NJA GJG (GIA)
Anton Nash LLC, Appraisers & Consultants
Colorado Springs, CO
(719) 648-1361


#5

Dear Bill: I imagine you are going to start a long and exciting
thread on this topic, “stone in place casting”. My two cents is as
follows: Boric Acid is an excellent insulator of heat and acts as
a barrier to protect the stone through the casting process.
However, from our experience, if the protecting ingrediants are
added to the investment in the proper proportions, it seems to
be more reliable. Try Ransom & Randolph’s “Solitaire”. A happy
by-product is that the casting surfaces and even better than with
their Ultra-Vest. RG


#6

Roger: If I may jump in here, cluld you please give the number of
Ransom & Randolph? I’ve always used Kerr’s investment. Is the
"Solitare" investment you reccomend especially made for
stone-in-place casting? Any info you care to share would be
appreciated.

Best;
Steve Klepinger


#7

Steve, Call United precious metals also, they have an excellent
few pages written about this whole process. Even have great
alloys speifically for this, like their VHF2. Very fluid, ideal
for casting at lower temps and has great fill properties. Very
Viscous.

1-800-999-fine
Best Regards.
Neil George

#8

Dear Steve: R&R can be reached at 800-800-7496. The "Solitaire"
was developed by R&R with our assistance as we belived the best
way to accomplish stone protection is in the investment itself. I
know customers going as high as 1350 F burnout, but one must be
careful as the temperature in the flask differs from the air and
without a recorder on the furnace, you must use extra caution.
Good Luck! RG


#9

If anyone has any stone in place casting tips, I would be greatfull!
Thanks Moe


#10

Hi Moe, if you search the archives there should be quite a bit in
there. We covered it fairly extensively there for a while. Mike.