Back to Ganoksin | FAQ | Contact

Platinum Casting


#1

Hi ya’ll, I’m wondering if anybody out there is casting platinum in their
shop? I’ve got the full setup, heating with hydrogen, etc, but am having
one primary problem. I’m running my gas at about 50psi and my O2 at 60psi
for a nice quick melt, but the pressure from the torch is literally blowing
my metal out of the crucible. I’m using 95/5 iridium alloy, but I’m
thinking even with a lower melting cobalt alloy I’ll still have the same
basic problem. Another more minor problem is that the carriage holder on
my caster wants to melt away during the melt. I’m using a rosebud tip, so
it’s possible a smaller tip would alleviate the heat spread, but probably
not the pressure. Any ideas would be most appreciated. Thanks, Mike


#2

Hi, Mike! Are you using a Wesgo Melting Crusible for the platinum? For
smaller melts, use a single port tip and set the oxygen regulator at 50
PSI. --Barbara Bequette


#3

Hi Mike, I also use H2 & O2 for Platinum melting, however I use about 18lbs
H2 and 40lbs of O2. I still chase it around the crucible sometimes. But not
so much with the lower Presures. How much Platinum are you melting at one
time? J.A.


#4

Hello Mike!

We cast about 3 or 4 plat. castings a month. I yearn for more information
too. More later.

Are you using Wesgo crucibles? That may help. I don’t know if others are
sold, but we haven’t had problems (with Wesgo crucibles) other than normal
replacement. I wonder if your crucible is a shallower design than the
Wesgo. Or if you have a Wesgo that is too shallow. There is quite a bit of
force from the torch and I am aware of your circumstance, it must be the
crucible design. The oxy. regulator will only give us 25 lbs. pressure
max., so that is what we use for pressure. I would guess our melt is
complete in under 3 minutes. The crucibles break down quickly so I’m told.
You might try reducing your oxy. pressure and see if that reduces the
flame pressuring your metal out of the crucible.

I have used the 95/5 but think it is more difficult to polish. Overall I
actually like it better, except polishing. Especially lapping. Seems to
drag even after going to the finer micron paper (guessing 1200 is my
finest). At work we use 90/10 and our surface skin varies. Not only from
thick or thin pieces does our results vary. The quality of the surface
skin varies for no apparent variable. We are using Astrovest.I have talked
to Mike Kelly at R&R with all OK as to our mix and burnout specs. How
about you? Have you tried the newer investments? Any tips you can share
would be appreciated.

Thanks, Tim


#5

Dear Mike,

I’m sure that I will not be the only one answering your thread. I cast my
JA certification ring two weeks ago in platinum and it turned out great. I
hope Jergen will also coment on this thread.

I used propane and oxygen for my fuel with oxygen pressure at 40 lbs and
propane at 5 lbs. Both valves on the torch control the flame. The oxygen
valve was totally wide open and the the propane valve controling the
flame was almost wide open. This gives you the oxydizing flame necessary
for the melt.

My metal of choice is 90 / 10 platinum irridium for torch melting.

I use the casting machine that spins like a ferris wheel with the tension
spring wound as strong as you can.

It sounds like you over heated your metal. It should spin and be moved by
the flame of your torch. It shoud not be blown out of the melting
crucible. It looks like a ball of mercury when molten. The torch just
chases it around the melting dish.

Your melting crucible needs to be a Wesco quartz melting dish. The dish
itself melts and contaminates the platinum about 200 degrees hotter than
the melting temperature of molten platinum. So the liquid window of your
melt is temperature critical. This means if you overheat your metal you
melt the crucible into the metal as a serious contaminent. This will leave
your casting totally brittle and will crack if you breath on it.

The only torch I have used is a genuine platinum melting torch sold in
most catalogs. Kind of like holding a rocket ship engine in your hand as
you melt. I have not used hydrogen / oxygen.

Platinum cobalt will probably not work with the torch melt. It needs the
argon atmosphere to prevent a lot of carbon related problems.

I don’t claim a lot of expertise here, but I have cast platinum
successfully. I guess I do it for the challenge.

Best Regards,
TR the Teacher & Student


#6

Casting platinum with the torch is actually a very good method to cast.
With experience, outstanding results can be achieved. The preferred way is
to use Hydrogen and Oxygen, with a multi-tip torch. Set the tank pressure
for both to 50 PSI. Open the hydrogen valve on your torch , so that the
flame is about 8 inches long. Now add oxygen until the flame is no longer
than 4 inches, with the cones on the rose bud to be about 1/4-1/2 inch
long. Aim the torch at the top side of the metal ( closest to the hole in
the crucible in the back ) and slowly pull the flame toward the front of
the crucible. As you do that, increase the amount of hydrogen very
slightly. Notice that the flame is entirely inside the crucible, about 1-2
inches away from the metal. After moving the flame from back to front three
or four times, the metal should be molten. At this time, have someone load
your flask into the machine, make sure all is clear and release the machine
to cast. The entire process, from the time you aim the torch at the
platinum, until the casting starts should take less than two minutes. (
about one min/oz) A lot of times, one tends to make the flame too big.
This results in all sort of problems. I get calls where torch-tips have
come off and fell into the melt, a result of too long a heat exposure to
the torch from reflective heat and a tip that was soldered to the torch
instead of screwed. The crucible begins to melt, again a problem with to
big and too unfocused a flame. Another problem is, that the flame is too
strong. This results in the dispersion of the platinum into little beads
and one will then chase the beads to get one single rolling piece of liquid
platinum. This prolongs the process, allows fused quartz from the crucible
to become part of the melt and creates all sort of problems. So use a
smaller flame, start from the back of the metal and melt the platinum as
rapidly as you can. Hope that helps

PLATINUM GUILD INTERNATIONAL USA
Jurgen J. Maerz
Director of Technical Education
JA Certified Master Bench Jeweler
http://www.pgi-platinum-tech.com


#7

Does anyone have any recommendations for someone who does
Platinum casting in the Dallas area ??


#8

Mr. Christianson, We would be happy to help with your Platinum Casting
project. We have been casting platinum for the past ten years. Our
turnaround time is 24 hours, cast and semi-finished. Please call with
any questions.

Brent Boling
B&B Craftsman
Custom Jewelry Design
Platinum & Gold Manufacturing
972-661-2044
888-PLAT18K
bbcraftsman@airmail.net


#9
     Are there any platinum casters out there who would consider
taking this on? Or this something that is best avoided for some
reason?  Is there some technical reason why you can't mix old with
new platinum? 

Dear Brent, PM West has been providing a platinum casting service for
many people and they are very easy to get along with. Now, the issue
of using your customer’s band or not, has several likely reasons.
First is the contamination issue. The band’s alloy may be something
like a 10%-5% Iridium 90%-95% Platinum. A lot of platinum casters
use a Cobalt/Platinum alloy because the melting temperature is a
little lower and it has a slightly wider liquidous and solidus range.
(fills better) If this were the case they would not want to mix the
alloys because it would then instantly make the button, sprue, and
gate instant refining scrap.

Another issue with this is the possilbity of the band containing a
solder joint. However unlikely, it is still a possibility that in
some past event, it was sized or repaired using a solder instead of
fusing original metal. In this case they are just erring on the side
of caution.

The last issue is that most casters including platinum casters get a
premium on the metal that they sell to you. By using your
customer’s metal to defray the costs then is also eats into their
profit margin for the same amount of risk. Not particularly good
business practice to do the same labor, take the same risks, for less
total money. No?

Give PM West a call in Los Angeles, CA and see what they have to
say. Maybe they can help you.

PM West
608 S. Hill St. #407
LA, CA 90014
(800) 999-7528

Best Regards,
J. Tyler Teague
JETT Research


#10

Sorry if this is a FAQ, but I would be appreciative of some advice
about casting a platinum wedding band for myself. I work in a
department which is familiar with metallurgy, but Are there companies
from which I can buy an investment mold of an appropriate size?

Concerning the mould material, do I have to worry that I am casting
platinum rather than gold? On other words, can I buy a mould which is
suitable for gold and just use it for platinum without any problems?

An I going to get adequate flowing of metal if I pour under gravity
(I do not have access to a vacuum caster)?

How best to ensure that the casting is sound?

Any advice would be appreciated. My intention is to cast my wedding
ring in a public lecture so I would like to try to get this right!

Thanks

Roger Reed

Roger C Reed
Professor and Chair of Materials Science and Engineering
Dept of Materials
Imperial College London
Exhibition Road
LONDON SW7 2AZ, UK
Tel: +44 207 594 6766
Fax: +44 207 594 6757
e-mail: @Reed_Roger_C


#11

I can’t tell you where to look in London, but there are plenty of
people there who do platinum casting. Call them up, give them your
wax model, and have them cast it. I appreciate that you are a
learned man, but this is beyond that.

A: There are no “Investment Molds” ready made - investment is poured
around a specific casting.

B: Gold and platinum are certainly not the same in any way
(techniques).

C: You absolutely cannot pour a platinum casting, and if you did,
you’d be taking your life in your hands.

Aside from the expense - casting your own ring is going to cost you
triple the price (@520 BP) because of spruing and button, the
technical issues are profound. To successfully cast platinum
requires a heat something like 200 - 300 deg. C. above the melting
point of stainless steel. Your audience will all have to wear goggles

  • it’s hot like arc welding, and doing the work is not for the
    inexperienced. If you tried to pour it, it will be solid before it
    hits the investment. 1800C. hits ambient air temp.? It’s like trying
    to pour molten lead through dry ice - not going to happen. If you
    asked about casting a gold ring - ok, that’s doable with some setup,
    platinum requires (REQUIRES) more.

#12

Hello Roger,

Perhaps, Brian Adam would be the one to chime in here? You should be
able to dig him out of the archives, if he’s not watching this…

You are not likely to be able to cast platinum in front of your
wedding party. You certainly won’t “pour” it into a mold - HOWEVER,
you could pour gold or silver. AND you could do it as I believe Brian
Adam has done… by hand carving the form of the ring into a tree
stump. There will be plenty of drama - flames and smoke during the
process.

If I were to perform this feat in front of an audience, I would
definitely seek advice from Brian - and I’d make a trial run (or 2 or
3) to make sure of the results and check the safety hazards. It is
probably not socially acceptable to splash your guests with molten
metal at a wedding…

Sorry about the platinum, too hot, too finicky for what you have in
mind. You could simply cast in silver using the above method, not say
what the metal is. The weight and thickness resulting from producing
a casting by this method might lead your audience to assume whatever
you wish…

Brian P. Marshall
Stockton Jewelry Arts School
Stockton, CA USA
209-477-0550
instructor@jewelryartschool.com
jewelryartschool@aol.com


#13

Hello Brian

Many thanks for your message. Since sending my original message, I
have been doing a lot one more reading and this (and indeed your
message) has convinced me that this is not as easy as I had hoped.
This even for a Professor working in an engineering department who is
supposed to be an expert in metallurgy…

I have this weekend investigated in a used centrifugal casting
machine which I found in e-bay. I am going to talk to a few experts
in investment ceramics - seems likely that I need to think carefully
about the choice of material for this.

I would be very interested in communicating with Brian Adam - perhaps
you have an e-mail address for him?

By the way, out of interest - why doesn’t the jewellery industry use
more rhodium? This is more expensive than platinum so I would have
thought there would be a market for rhodium wedding rings. Just a
thought.

Thanks again

Roger Reed

Prof Roger C Reed
Chair of Materials Science and Engineering
Department of Materials
Imperial College London
South Kensington Campus
LONDON SW7 2AZ, UK
Tel: +44 207 594 6766
Fax: +44 207 594 6757
e-mail: @Reed_Roger_C


#14
    By the way, out of interest - why doesn't the jewellery
industry use more rhodium? This is more expensive than platinum so
I would have thought there would be a market for rhodium wedding
rings. Just a thought. 

We DO use a lot of it, but as an electroplated finish over other
white metals. By itself, not only is it perhaps TOO expensive, but
it’s virtually impossible to actually work the stuff. Nice thought,
but there has to be some practical way to make a wedding band for
the average jeweler who may not be equipped quite as well as a NASA
research lab… (grin) And then when you’re done, it’s useful to
have a piece of jewelry that can be serviced, such as when the
customer needs it made a bit larger or smaller. Hightly brittle hard
metals don’t make as practical jewelry in this regard. There are
firms doing wedding bands in carbide, that suffer from this
limitation, but their raw materials isn’t so costly as to make the
things totally impractical… (just don’t drop one on a concrete
floor. Pretty hard stuff, but brittle too.)

Peter


#15

I can’t believe that what you are suggesting will work. there are so
many levels of complexity here you have no reall concept of what you
are considering doing. I admire your willingness but this is highly
difficult. Don’t think that I am being rude. To start, you need a
centrifugal casting machine made especially for Platinum. The heat
required to get Platinum to flow is extremely high. You will need a
very strong torch, probably not advisable in an auditorium. The
liquidous to solidus for Platinum is so brief I can’t imagine it will
work to simply do a gravity pour even if you got to temperature. As
for the casting mold you seem to be rather out of your
league here as well. Unless there are differences in what is
available in Britain, you need to carve or buy a wax, then you need
to use the appropriate investment material, this is a totally
different type of investment. It is really a ceramic and not a
plaster type of investment. It has to be mixed correctly and has a
different cycle for burnout. All of this requires somewhat
specialized equipment. Also, if your casting where to work you will
need to break the mold away from the casting and usually soak it in a
highly dangerous acid solution to remove the last bits of investment.
There are some investment s that break away better now but still, it
is all quite complex.

There are so many dangerous aspects to this venture. I hope that you
reconsider even attempting this venture. If not, I suggest you hire a
professional to help you sort this out. Perhaps they can make your
idea work for you.

Good luck Dennis