Pt/Co 950 is indeed magnetic. It should be soldered with 1700
solder if you are sizing it. Roll your solder through a rolling
mill and make it very,very thin. Then wedge it in between the
seam and heat with a direct, oxidizing flame and solder. Use #6
eye protection. The alloy will slightly discolor during this
process. AFTER IT HAS COOLED DOWN, cover the ring with fire-coat
(Boric acid/Alcohol mix)and heat to about 900C or a bright
orange color. Then pickle it and the slight oxidation is gone. If
there is no recess area , it can also just be polished off. DO
NOT EVER USE flux when you heat Platinum to these high temps. The
borax or fluoride will enter the metal and contaminate it,
causing imbrittlement… This is the reason for NOT fire coating
it before the operation.
Pt/Ir is the standard in the US and is a very good metal, as
100% of it is PGM (Platinum Group Metal). It can be welded and
soldered at will and is very forgiving. Again DO NOT USE FLUX.
Fluxes are designed to work in the 1000 F range. (some more, some
less) the purpose is to keep the soldering are free and clear of
dirt, oxidation and such. PT/Co does’nt START to oxidize until
about 1200 CELSIUS. way out of the range of effective fluxes.
Pt/Ru is a wonderful alloy, designed for machining, die striking
and such. It is rarely cast and does not have very good casting
characteristics. Pt/Co is by far better. (see “the Platinum
Manufacturing Process Issues 3 and 4”)
Other alloys for casting in the US are Pt/Co/Cu. This Alloy has
the fluidity of Cobalt but without the magnetic properties. It
was developed by Engelhard-CLAL. Platinum alloys for export need
to contain 950 part per 1000 platinum, as that is the standard in
most countries. In US the standard is different.
An object made of PGM can be CALLED PLATINUM if at least 950
parts per 1000 are made of PLATINUM GROUP METALS, of which AT
LEAST 500 parts are platinum proper.
An object made of PGM can be STAMPED Platinum, if that ENTIRE
950 parts is platinum proper. It can also be stamped Pt950, Plat,
950 Pt or 950 Plat.
If an object contains between 850 and 900 parts per 1000
Platinum, the difference between that and 950 MUST be a PGM (
Iridium, Ruthenium, Osmium, Palladium, Rhodium), it can be
stamped respectably Pt850 or 850 Pt or 850 Plat. 900 Pt, 900 Plat
or Pt 900. The old marking IridPlat or 10% Iridium90% Platinum,
while still legal, are no longer being used.
Under 850/1000 Pt alloy MUST identify the alloy composition in
PGM to be legal, so , if you were to make a ring with 600 parts
per 1000 Platinum, the 350 parts that make the 950 mix must be
identified. You would stamp it Pt 600 Ir 350 or some such.
950 Alloys need not have anymore precious content to make up the
remaining 50. This is done , so that one can create a purpose
alloy, i.e. give it different properties. In Germany the work
horse alloy was 950 Pt/Cu. the copper gave it hardness and
ductility as well as malleability. It was an O.K. casting alloy.
Then in recent years the switch to Cobalt occurred, because
Cobalt is a grain refiner, makes the platinum wetter and thus
Other common 950 alloys are Pt/Au, Pt/W, Pt/Pall etc. As
platinum is a dominant metal, the color does not change visibly
through these alloying techniques. Alloys are given different
properties. Some can now be heat treated, others are springy and
others machine well.
Working with platinum requires product knowledge. Know what the
alloys can and cannot do and dont use gold techniques when
working with them. Think of it like Diesel vs Gasoline. While
either will propell a vehicle, it is done in a different way.
Platinum is NOT difficult. It is Different.
Hope that helps.
Have a Platinum Day
PLATINUM GUILD INTERNATIONAL USA
Jurgen J. Maerz
Manager of Technical Education
JA Certified Master Bench Jeweler