Hi Orchidians: If you folks haven't tried these new plumb
platinum solders yet,..... Stuff is expensive, about $52 per
pennyweight, but I think in my case (retail jeweler), it's well
some suppliers are cheaper too. We paid 48 a dwt…
There are two alloys, one melts at 1300 degrees centigrade, the
other at 1500.
There’s also, at least from our supplier, a third alloy, melting at
1400. On the ones we got, the three aren’t marked as to temp. They
are just marked PTE (easy) PTM (medium) and PTH (hard)
There are also difference between the three grades as to pt
percentage (the 1300 is 900 pt, the other two are 950. Plus color
varies slightly. I find the 1400 is an almost perfect color match for
900 iridio platinum. Even a somewhat sloppy flow of the stuff, say to
fill some pits or the like, when polished, is virtually invisible.
the 1300 and 1500 are still slightly visible as faint color
differences (The 1300 is faintly darker than the platinum, the 1500
actually slightly ligher color, or so it seems to me) With a good
tight seam, though, none will be an easily visible color difference.
hardness, Re: not polishing it out of seams, is a good match with all
three. Actually, I think the solders are slightly harder. Or at
least, the solders work harden more quickly. But not to a degree to
cause problems. plus, though i don’t have data to back it up, I think
the strength of the joints is superior to that of "conventional"
there are, though, a couple other differences. When these solders
melt, they tend to oxidize a bit, kinda like the way cobalt platinum
does when heated. Polishes off, of course, but initially, the joint
looks a little grey and cruddy, especially where you placed the solder
paillon, where it leaves a little bit of a “scar” to be buffed/cleaned
off. The solders tend to be a little bit more “sludgy” when melting
too. A wider range between liquidus and solidus temps, plus that
tendancy to oxidize, means that sometimes it will seem that the solder
has not melted and flowed, when in fact it did so, but there remains
a slight raised scar that did not flow in. Some of this depends on
the flame you’re using. With traditional platinum solders, you can
use a highly oxidizing flame with little difference between that and
an only slightly oxidizing one. With these new solders, I find it
works better if the flame is only barely oxizing. Also, I find it
slightly more difficult to see the solder actually flow when working.
I think it’s because of that slight oxidation, which makes it harder
to see shiney flowing metal. It’s possible this is just my eyes.
But through those dark green lenses, it’s hard enough, sometimes, to
see quite what’s happening, and with these new solders it’s slightly
more difficult to judge when the solder has completely flowed.
Usually, what I find is that I don’t think it has flowed through the
whole seam, only to find, on cooling, that it did in fact flow just
fine and I couldn’t tell that fact “at temp”. Finally, though this
wasn’t mentioned in the sales flier from Frei and Borel, I note that
the refiner we got ours from (these are the same alloys as F&B, by
the way) mentioned that you must be especially careful NOT to allow
flux or borax or boric acid to contaminate the solder area. It can
cause brittle joints. So too, can the use of tungsten or tungsten
carbide soldering picks or tools with the molten solder. That means
you must solder the pieces simply by placing the paillons and heating.
Don’t use a poker to solder unless the poker is platinum.
The upshot is that these solders make the soldering operation a bit
more difficult. In particular, the inability to use a poker means
you’ve sometimes got to balance a bit of solder in awkward ways and
then try to keep the flame from blowing it away. But you get used to
it quickly enough, and the dramatic improvement in the end result with
regard to color and hardness and strength of the joint seems well
worth both the extra cost of the solder and the slight extra bother in
using it. I’ve pretty much switched for almost all new fabricated
work, and most repair work too, with the few exceptions of those
repairs when I really do need the lowest melting solder I can find
that isn’t quite yet a white gold solder, and am then using 1100 or
so. These situations are generally rare, however. Fortunately too,
since 1100, in my book, is not too different from lead solder on gold.
Don’t believe me? Solder a wire to a piece of sheet with 1100. Neat
joint, not flooded of course. Leave enough wire end exposed/not
soldered so you can grab it with pliers. do so and pull. You’ll find
you can peel it back off the sheet metal just like opening a sardine
can with those little keys. this is still better than the strenght
of a gold solder to platinum, but only just barely. The thing is that
with 1100 and other really low temp traditional platinum solders,
there is a poor enough alloy match, and a wide enough range between
the melting point of the solder and that of the platinum, there the
solder really just wets the surface of the platinum, without really
penetrating into it at all. With these new solders, since even the
1300, which would otherwise be a somewhat low melting mediocre
platinum solder only barely acceptable for new work, the solder is
still a 900 platinum alloy, and there seems quite enough penetration
or the joined pieces to affect a nice strong joint.