Iam taking a wild guess here but Iam thinking your metal temp
exceeded the temp of your heads.You may have compromised the alloy in
the heads.How were they cast?Vacuum,Centrifugal?It is very hard to
judge the temp of your metal.You should have better luck using gold
make sure your alloys are matched.I believe most cast in place pieces
now days are done using induction casting.This would at least give you
a more controlled environment to work in.
Janet, The long heating at high temprature has caused the crystals of
the silver to grow to huge size and the grain boundaries between
crystals have grown as well this is causing the resulting metal to be
very brittle and crack at the grain boundaries. Try setting the
heads in the wax and then remove them before casting and solder them
in place on the finished casting.
Jim
James Binnion Metal Arts
@James_Binnion
Member of the Better Business Bureau
Hi Janet, for what it is worth I too used wax heads when I first
started and cast them in place thinking how great and easy it was .
Now that I have more than 20 years beyond that personal insight my
suggestion would be not to. My biggest concern was the porosity of
the metal in the prongs of the cast head. I just couldn’t trust the
strength of the metal and risk loosing a set stone, not to mention
the pain of cleaning up each prong in a tight cluster after the
casting. Good luck,
jim
Someone mentioned “I believe most cast in place pieces now days are
done using induction casting.” This may be true due to the fact that
the large companies only have induction…, However , to assume that
induction is far more accurate is not neccessarily correct. When an
Induction machine that will melt your metal in 3 minutes melts, it’s
putting out some serious horse power to do so and as a result, on the
first pass, these machines tend to overshoot the melting temperature
by quite a bit, then, after a minute or 2 they stabilize ( more or
less) .This is why these machines work best using fresh gold and why
they are always sending metal out to refiners …They don’t get the
reuseability that torch casting offers if done right.We have never
sent gold or silver out for refining ! I’ m sure to catch some flack
from the companies that sell induction machines !
I believe that if you ran a pole , you would find that people who buy
raw castings from large production houses get quite a bit of porosity
in their castings( varies depending on how good they are and how much
care is taken)Most of my customers used to deal with larger casting
houses and their
major complaint was porosity .
I digress, Back to the main subject. If you want to cast a setting
into a different shank, you must be careful of
the quenching times dependant on your alloys. Copper based sterling
will be soft and maleable if quenched at the 10 minute mark after
pouring.Hard and probably brittle after 20 minutes.
Non - tranishing silver will be brittle if quenched at 10 minutes ,
but malleable at 20 minutes.
Most 14k gold alloys will be fine quenched at the 20 minute mark .
Most white gold alloys are best quenched at the 10 minute mark.
This may solve the brittleness that some people experience.
Daniel Grandi
Hi Janet, It’s been a long time since I jumped into a thread. The
folks answering the queries here are doing a great job. To get to the
subject… Most heads purchased from findings suppliers are die
struct…meaning they start with sheet metal of a specific alloy and
drop forge them into shape. ALL metal in jewelry begins with casting.
To make the sheet metal they start by CASTING an ingot and then roll
mill it into wire, sheet or other stock. This milling process crushes
the large crystal stucture in the metal making a long grain thereby
giving it stregth and density. You can take a piece of rolled metal
and bend it back and forth many times before it breaks. Cast metal,
such as your cast heads, will break after fewer bends. My advise to
the designers that I cast for is not to mold a store bought metal
head. If you want a mold for consistant good casting results,
fabricate a thicker head for your model so in your final casting you
will have extra metal and therefor strength to work with. If you are
carving the master model in wax add the extra in wax as well. You can
take a manufactured plastic head and dip it into hot wax to beef it
up. Cast prongs are used all the time in top quality cast jewelry.
Alloy choice is also a factor for brittle prongs. Adding silicon to
gold alloys has been very popular and will result in a pretty casting
on the outside and poor crystal adhesion (prongs break). As it is
every where else: beauty is only skin deep. Skip the alloys with
silicon. Once you have the proper thickness and the proper alloy, the
next important consideration is proper spruing, then your kiln and
flask temps, then your metal temp at flow. Adding a metal head to a
wax and then casting is very tricky indeed. the problem occurs in the
investment and kiln. Investment has sulfer in it that will encourage
the metal to oxidize and there is oxygen present in the kiln as well
combined, these factors will prevent the cast metal from fusing to the
metal head. The best you can hope for is to have the cast metal lock
the head in place, still in can end up loose. This seems to be a lot
of work to save a little. Fancy casting equipment will not solve your
casting problems. I have seen some of the best casting done on the
most rudimentary equipment. Your knowledge of the materials and
process will lead you to success. Happy casting!..John,
J.A. Henkel Co.,Inc. Moldmaking Casting Finishing
To Janet and all, I did not pay a lot of attention to this thread
until I read today’s posts, and thought I would add my two cents
worth. My uncle started this small casting company in 1959, and I
bought it from him twenty years ago. In all that time, we have
produced a line of cast heads that have been very popular with many
"old time" diamond setters throughout the midwest. Almost all the
heads we ourselves use in our own retail store are these same cast
heads, and generally we find that we have far fewer failures with the
cast variety than with die struck.
The properties are different, and I would never try to open a head,
remove a stone, and re-bend the same prongs. They are by design,
however, a heavier prong and give the customer longer wear life in
general. The pear shape and marquise heads all have the V type ends,
and the round stone heads are more stable and less likely to bend
while cutting stone seats.
We always quench the metal in alcohol as soon as the red color
dissappears, and strongly prefer them over a die struck head. If I
can offer any other contact me off-list.
JMF
Fayrick Mfg. Inc.
Dear Mr. Grandi, (and all other Ganoksin websiters), I sincerely hope
you do not catch too much flack from the induction casting machine
makers, yet I would like to dispel the rumor that all induction
machines work on the principal you described. There are many
induction machines available today that cast “on the way up” and do
cast at the set-point. Most of these machines are more accurate in
temperature, and are also in a closed or inert gas system (no oxygen
present) in the melting and pouring areas than that of any type of
torch melting units.
As far as the time cycle issue, a three minute time cycle is actually
very good for most alloy compositions. The longer the metal is
molten, the more chance you have for the material (alloy components)
to separate, and in some cases vaporize from the metal make-up. I
know of a few different manufacturing companies that use different
induction machines that never send the metal for refining…actually,
the only metal they send back is floor sweep and the like.
Porosity issues are caused by so many factors that to blame it on
fast time cycles from an induction machine is, in my opinion,
completely unwarranted. Spruing, gating, treeing, metal and flask
temperatures, pattern design and a whole host of other issues can
result in the amount of porosity a piece may have.
In my 20 years in this business, I have been through the various
casting processes and have learned that good results can be achieved
using most types of machines and procedures. It all comes down to
following procedures and insuring that each step along the way is done
using tested measures with consistent application of procedures.
I would hope that anyone considering stone-in-place casting remember
to research all options and get as much as they can before
making any decisions. Casting is actually a very fun “game” and I
would like the oportunity to talk to anyone that might have more
questions. I can be reached at @Joe_Lovato.
Sincerely,
Joe Lovato
Neutec/USA
Regarding casting heads in place.
I haven�t been impressed with any cast in place settings I have seen.
I prefer the following method, as it is cleaner and doesn�t destroy
the quality of the heads.
Put the almost completed wax ring on a mandrel.Using a heated wax pen
or dental tool, heat up the polished metal head* and sink it into
the wax, using the hot tool to move the setting around until it looks
good. As soon as the setting is in the right place, blow on it to
cool it off (if I�m in a hurry I will squirt a bit of water on it).
It is very important not to jar the setting while it is cooling- that
causes the wax structure to weaken. When the wax is cool, I use my wax
scraping tools to blend the wax in around the setting. By the time I
have the wax finessed I can usually gently rock the setting to break
it free from the wax. You will see a shiny surface on the wax where it
was in contact with the setting. Do some final touch ups on the wax
and cast it without the head.
- If the setting has a lot of pierce out work, undergalleries etc�
fill up the inside of the setting with Heat Shield Compound before
heating up the setting to sink it into the wax (from Small Parts Inc.
1(800)220-4242 Heat Shielding Compound #R-SO-FH6 costs about $12
for a jar that should last you years.)
After the piece is cast, clean up the cast ring and make sure the
setting fits well to the ring (with the heated head technique it
should fit pertfectly). Then crazy glue the head into the cast
mounting. Pack a small amount of Heat Shield Compound aroung the top
of the head and ring (not a lot, just enough to support the ring and
the head). Then flux up the inside of the ring/head. WITH GOOD
VENTILATION and a mini torch heat up the seam- when the flux flows,
put a chip of solder on the seam and it flows beautifully. Crazy glue
acts as a flux- works like a dream. When it cools, dip in water, the
heat shield compound washes right off, now you can pickle and polish. I
hope this helps�. Kate Wolf in spectacular Porland, Maine