I have been doing platinum work for about 15 years now and I just
accept the fact that you will see a seam on most work. I try to
use hard solder when I can. This week I was not at my shop with the
oxy-propane so I did a sizing with pt 1000 solder and boy did I
see it.
Yeah, you would. That’s way too soft a solder for almost any sizing
job. Remember that classic platinum solders contain little if any
platinum (the highest melting ones, 1600 and 1700 have some platinum)
being instead, alloys of palladium, alloyed I think, with gold or
silver. The result is a much softer metal with a darker color. It
mechanically is OK with platinum (though your 1000 solder is not a
strong joint, especially for a butt joint like a sizing), but the
color and hardness is all wrong for any sort of decent appearance.
...I then went back through the whole process and used a soft goat
hair brush for the final polish...........but it still showed up.
You might, if the original seam was really tight and well done, be
able to burnish the seam. Sometimes this will mush around the metal
enough so a seam doesn’t show so much. Same as closing up porosity.
But it’s not the best way.
I know why I see it, the metals are different hardnesses and the
solder 'pulls out' when polished. I am looking for a magic bullet.
If anyone can give it to me, i will give them my grandmothers
recipe for Maryland crab cakes... this means YOU MR. Binnion.
You can share those cakes with Jim and me both, please (grin)
Two methods. One is to weld the seam. Not all sizing joints can be
done this way, but the classic weld for sizing is done by rolling a
bit of platinum very thin, cutting a bit of this that measures
slightly wider and longer than the width and thickness of the metal
of the shank. Close up the seam so it’s tight enough to hold this
shim in position, so the shim fills the seam and extends out a little
all around the seam. Using a sharp hot flame directed right at the
shim, you’ll find that platinum’s poor heat conductivity means you
can fuse that thin shim just a moment before the shank itself starts
to melt. When it’s edge melts, it continues down in a bit, welding
the two sides of the shank. Repeat this for all four surfaces (both
sides, inside, outside, etc.) With practice, this gives you a welded
joint that has no seams at all.
The other method is suitable even for those shanks that are not
going to be so easy to weld this way (thinner flatter shanks, or the
like). That method is simply a better type of solder.
For close to ten years now, you have been able to buy a “plumb”
platinum solder. At today’s platinum prices, this stuff isn’t cheap,
of course, since a pennyweight of the solder contains not just the
alloy constintuents, but as much platinum as your basic platinum
itself. it comes 90 - 95 percent pure, the remainder (what lowers the
melting point to make it a solder) is germanium and indium, if I
recall. PMWest is the company that developed it, and it’s sold by a
number of metals dealers in addition to them.
The plumb solders are a bit harder to use than traditional junky
solders. They don’t flow quite as easily, and tend to sometimes leave
a bit of a scar, the remainder of the solder piece, at the surface of
the joint where the paillon was placed (especially with the easy
grade). But color and hardness of the finished joint is a perfect
match, and even if it sometimes looks like it didn’t completely flow,
in fact, it will have done so. Just put the paillon where you can
clean up any residue afterwards.
The plumb solders are available in “easy”, which melts around 1300,
“medium,” which melts at 1400, and “hard” which melts at 1500. I find
the easy grade a bit difficult to use, since the solder sheet is
often very hard and brittle, and simply cutting up bits to use is
tricky. The medium and hard grades are more friendly that way, and
actually flow somewhat better than the easy, though at their
respective higher temps. I generally use the medium grade for most
work, as it’s the best color match for the 10 percent iridium
platinum I normally work with, and it’s generally suitable for almost
all my uses. Occasionally with a complex piece I’ll use the easy for
the final assembly, but I try to avoid it, as it’s just not quite as
nice to work with. The hard grade, even though higher melting, is
also nice to work with. Unlike gold solders, there is little
advantage to the higher melting solders for purposes of appearance
or strength. All three grades are “plumb”, and offer similar finished
strength and appearance. So use the stepped temperature grades only
for when you need a difference in flow point. This differs from gold
or silver solders where the higher melting solders also offer a
better quality joint.
While I do keep the traditional platinum solders around too, at this
point they’re reserved for those repair jobs where I really need that
low temperature solder, and this is rare, since mostly I do the
repair jobs with the laser welder anyway. But still, it sometimes is
still a valid choice, so long as you accept that you’re soldering
platinum with a palladium alloy that doesn’t match. The real main use
I now have for the palladium based platinum solders is much more
understandable, and that’s when I need to solder palladium itself…
Those solders work very well for that.
For platinum work, though, I pretty much have totally switched to
the plumb solders. They solve all sorts of problems.
PMWest’s links regarding this solder:
http://preciousmetalswest.com/platinum%20solders.php
http://preciousmetalswest.com/developing_plumb_platinum_solder.php
Cheers
Peter Rowe
Seattle
He covered everything I