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Platinum Pits


#1

Have had two castings done in Plat/cobalt and where the caster
attatched the sprue I have had a large pit or cavity. Filling
this area in a manner that does not show in finished peice has been
a problem. I have ball burred the area and taken a rod of platimum
wire and solered into place using platimum easy solder but the
solder area shows up when done.

Does anyone have a suggestion? Ron


#2

I would try to wield a piece of the same kind of plat in place.
Solder usually leaves a line. I use the weld method often with
outstanding results. Hope this helps

Rick


#3
 I have ball burred the area and taken a rod of platimum wire and
solered into place using platimum easy solder but the solder area
shows up when done. Does anyone have a suggestion? Ron

Hello Ron:

Before setting stones or anything else, Take a small piece of the
platinum from the sprue and melt it into a ball a little larger
than the pit. Set it in the pit and heat it until it flows. No
Solder!!! I have had many of my castings come back with a pit in
the sprue.

Michael Mathews Victoria,Texas USA


#4

Have had two castings done in Plat/cobalt and where the caster
attatched the sprue I have had a large pit or cavity. Filling
this area in a manner that does not show in finished peice has been
a problem. I have ball burred the area and taken a rod of platimum
wire and solered into place using platimum easy solder but the
solder area shows up when don

Hi Ron,

Your best bet is to weld it. Ball bur to remove any of the easy
platinum solder, take your platinum wire and ball up the end so it
fits into the cavity and fuse it in place. The easy solder has
paladium and silver in it, so it always shows up darker than the
surrounding material. You need to use 1700c or higher to be
seamless. Remember, no flux or boric acid with platinum.

I have stopped using pt cobalt because we have had two complaints
about it being magnetic. We have been using 95% plat 5% ruth.

Mark P.
WI USA


#5
I have had a large pit or cavity.  Filling this area in a manner
that does not show in finished peice has been a problem

Dear Ron, I’ve been reluctant to comment on platinum postings
until now, it would be difficult to explain in reasonably quick
and terse way. I will try this time. Platinum solder has little or
no platinum in it. I believe it contains gold and other metals.
It is considerably softer than platinum alloys and has a
noticeable color difference. No matter what I’ve tried in the
past, I can never seem to get the solder not to show . Polishing
always reveals the seam or pit the was filled in. One must WELD
with platinum to fill in a pit. Welding, as we know, is much like
"controlled" melting, not terribly precise either. If the pit is
near a place were the “controlled” melting might jeopardize detail
or form, the I would use said solders or use 19 ro20K white gold
solder(whichever is more easily obtained by you). I, personally
prefer Hoover and Strong’s 20K white to Stuller’s 19K white, it is
harder and whiter- and it can be used near set diamonds. If it is
at the bottom of the shank or at some other area that can be
welded, I would first try to use a piece of the sprue and take a
small “pallion” sized piece and stick it to the pitted area with
Handy flux (or some other white paste flux). I,know,I know, Your
not supposed to use flux with platinum,but with the Cobalt casting
alloy, it seems to crud up and oxidize when welded without the
paste flux. Stuller has sent a technical advisory with the delivery
of their 950 Pt/Co alloy saying that it cannot be welded, but to
use instead their 1700+"welding " solder. I couldn’t disagree
more, their 1700 welding stuff doesn’t weld at all it just a high
melting point solder. Instead, using an appropriate #5 welding eye
shade, use an extremely sharp, hot flame. I’m talkin’ really
sharp and hot here, oxy. pressure at 20psi or more. I, should say
that this is why I put up with the notorious Hoke-Jewel torch;
with the rose-bud tips, either propane or natural gas, it can
produce the perfect type of sharp flame for this . Now, we’ve
applied the flux and stuck a “pallion” to the pit, then, bring the
sharp flame up to the “pallion” (from a distance) and watch the
pallion melt into sphere and become "highly " mobile. Continue to
heat the spot until you see it “collapse” onto the shank.
Immediately withdraw the torch flame and let it cool down. If
there are no stones in the ring you can quench it H2O. It might
take another attempt along with some heavy, heavy burnishing20
and you should be successful. I definitely try this out on some
scrap first though, as it does take some practice. If you have any
other questions, contact me off this site ; @elcraft.
Good Luck, Eben Lenz


#6

Hi Ron, Don’t use plat solder when repairing a pit. This is common
to plat casting. Ball bur a neat hole, then make a small ball to
fit as close as possible. Use a very pointed small intense flame
and fuse the seam. J.A.