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Platinum sizing


#1

Hi, all

On saturday, I had a real problem sizing a platinum engagement
mounting. It was an old mounting,probably 30 years, that was
plain but quite heavy (about 3 dwt). It was stamped 10per cent
irridium. I needed to make it about two sizes larger. I did not
have that width platinum in stock, so I ordered some from a
finding house,( i did not inquire if it was the new cobalt
platinum, and that could be the mistake). Anyway, I tried to use
platinum 1600 solder, and I did use very strong welders goggles,
so strongly protective, that it was very hard to see the ring
until it became white hot. When i was sure the solder fused, I
straightened, filed and sanded. At this point, the joint
cracked. I cleaned and tried again. It cracked again. I then
filed a piece out, and decided to weld with platinum from the
newly gotten platinum bar. The ring is finished, but I am not
happy. I don’;t know what i did wrong, plus I don;t care for the
seams I see left in the ring. Any ideas?

thanks, allan


#2

Allan,

Did you use flux or boric acid? If so thats the problem. Try it
without, and try 1700. I was having the same trouble until I
eliminated the flux and boric acid. Just use the solder or weld it.

Mark P.
Wisconsin


#3

On a couple of occasions I have seen palladium rings that
jewelers mistook for platinum. I don’t think that this was you
problem. I doubt that a finding house would send you cobalt
alloyed platinum as it is not particularly well suited to
rolling. My best guess would be that this shank was contaminated
with solder or possible gold. Without seeing it, it is very hard
to say. If I came up with seams on the second attempt, I think
that I would give it one more try, cutting the shank back
further, removing any stones as necessary and welding with
platinum rather than 1600. Purely a personal opinion. Bruce

Bruce D. Holmgrain
e-mail: @Bruce_Holmgrain


phone:: 703-593-4652


#4
  Did you use flux or boric acid? If so thats the problem. Try
it without, and try 1700. I was having the same trouble until I
eliminated the flux and boric acid. Just use the solder or
weld it.

Are you using sterling and what are you doing about fire
scale/oxidation??? (which the flux is supposed to avoid?) Many
times – I do the same thing you do . . .just solder.


#5

Hey! Alan, it’s usaullt easier to use a peice of flattened plat
than solder when you don’t know what you’ve got! and it’s more like
fusing than soldering. contact me and I’ ll explain further if need
be! GoldSmithy @aol.com


#6
 Are you using sterling and what are you doing about fire
 scale/oxidation??? (which the flux is supposed to avoid?)  Many
 times -- I do the same thing you do . . .just solder.

No, no, this is only for soldering platinum. As I have learned the
flux and boric acid react with the platinum at the high
temperatures used in platinum welding and soldering (1700 C or
more). This will cause the seam to crack. The platinum will not
oxidize. This is just for sizing and fabrication, soldering near
stones is a different matter.

Mark P.
Wisconsin


#7
Did you use flux or boric acid? If so thats the problem. Try it
without, and try 1700. I was having the same trouble until I
eliminated the flux and boric acid. Just use the solder or weld it.

Man oh man does eliminating boric and flux help. IF you use
oxy-acetylene push the O2 real hard. Stuller has a couple of
Tech Tip flyers with good info.