I do not claim to be some "expert", but I do know what I have learned
over the past 30 years, and I feel some clarification is needed here.
First, a soldered joint is NOT a welded joint. For platinum sizing,
a welded joint is preferable to a soldered joint. Learn the
1100 plat. solder is the lowest melting point (1832 degrees F) plat.
solder available. Also called "Extra Easy" solder. A low melting
temp. solder used to repair near other soldered areas. Not suitable
for a proper sizing joint. Easily buffs out of the joints and has a
noticeable color difference.
1300 plat. solder (2372 degrees F), "Hard" solder, is a good solder
to use for assembly work where no other plat. solder is present. I
have used this solder for sizing when necessary, but this solder also
polishes out of the sizing joints.
1700 plat. solder(3092 degrees F), "Seamless" solder, is the
preferred solder for sizing. Melting temp. is close to the melting
temp. of platinum (1774C, 3225F), so temperature control is necessary
or you will be welding instead of soldering. If that's too close,
1600 (2912F) solder works.
Plat sizing is much like white gold sizing. The highest karat
(fineness) solder must be used or the sizing seam will show after
polishing. Actually, welding the sizing joint is the preferred
method of sizing platinum, but a high fineness solder is acceptable
if done properly. Using the higher grade plat. solders take a bit of
practice and protective glasses must be used. Protective glasses are
highly recommended when soldering, especially welding, platinum
throughout the temperature ranges.
As to which torch is needed for platinum working, I have used a Hoke
torch, LP gas (Barbecue grill) and oxygen, for 30 years with great
success. The Hoke is capable of generating enough heat to melt
platinum while still allowing control of the process, which is
necessary when either soldering or welding, especially in the
presence of other grades of solder.
Flux and Boric Acid dipping is not advised when soldering or melting
platinum. Has to do with the high heat involved and the gasses of
the chemicals being absorbed into the metal leaving pits.
Using platinum solder around stones is not advised. Diamonds can be
damaged by the heat necessary to melt the platinum solder. If
in-place diamond tipping is necessary, use plat. stock with 18K W
solder. And be careful with the temperature.
If you are not familiar with working platinum, it can get to be an
expensive learning experience. Practice with a piece of scrap first,
and above all, use the welding glasses. The temperatures generated
produce a bright white light capable of damaging (permanently) the
<< If you suspect there is garbage solder, the first thing to check
is to see if the ring was sized down and not up. If it is sized up,
you're better off taking the insert off all together. Whatever is
there, file it all away including back from the joint to ensure you
only have platinum left. >>