I usually use files, then abrasives, then tripoli, then a plat
polishing compound on two different mops, and try to clean as much
as possible in between each stage. And I'm still not happy. I still
find tiny lines on the metal, particularly with flat surfaces -
these are invisible to the customer, but only just. With platinum
costing what it does, it deserves 20 mins, 40 mins, even an hour,
if required. And I HATE polishing platinum. If the customer wants it
polished, I expect to see a good reflection of my face in it. If
you've found a way of achieving that with two or three stages,
please help us all out - it would mean you've mastered the
technique of polishing.
While I agree that platinum can be difficult to polish, one key to
speeding it up and making it simpler is in the media you use to do
the job. I use four steps. The first is either some combination of
files or burs to get the shape, remove bumps, seams, etc etc etc.
Then an abrasive such as the 3M trizact abrasive drums or the
microfilm sanding films or drums or sometimes one or another of the
several 3M diamond drums or films. Both Gesswein and Stuller also
sell a really nice little premounted line of emery drums. Like the 3M
products, these are high quality uniform abrasives. From Japan, they
come in a range of grits all the way up to 800 grit. All of these
choices in abrasives are the keys both to getting an initial true
surface, and one which then eliminates the occurance of those pesky
lines that show up later, since their very uniform particle grading
means all scratches on the resulting finish are the same size, so
when it looks like you’ve buffed them all of, you have. None are
those deeper/larger ones that seem to stay hidden only until you find
them remaining at a later stage. The abrasive cleans up the coarser
file or bur marks. I could eliminate it with fine enough files, but
then it might take a bit longer. After the abrasive, don’t use
tripoli or greystar. Too slow, and not really so good with platinum,
even if lots of people still use it. Instead, try the Gesswein
platinum polishing compounds they import from Japan. These are all
micro graded aluminum oxide. Hard enough so things like solder joints
or the like won’t polish out faster. On the right buffs, brushes or
laps, the 800 grit platinum tripoli cuts fast. Fast enough that you
can, if you want, directly polish a rough casting or even fairly
coarse file marks, especially with medium or hard felt laps. But
that ends up not saving you time. Take enough time with the 800
compound. It’s perhaps the most important step. Be sure no ripples or
defects show. Use a loupe or other magnifaction if needed, to be
sure. This stage is the one that really needs the most time on it.
Get it right, and the next step, the 8000 platinum tripoli, also in
the same family of platinum polishing compounds from Gesswein, goes
as fast as any other rouge on gold. If you still have lines, it’s
because you didn’t do the 800 step right. The 8000 compound leaves as
good a mirror polish as most situations usually require. You can, if
you need the highst possible polish, finish with kissing the surface
with red rouge, or one of the other platinum rouges, but I find the
difference to be small, and often not needed on most work. Even so,
that adds only a moment or two if you do it. The nice thing about the
800 compound is that despite giving you a high polish, it also still
has some cutting ability to it, which helps with things like the
occasional stray bit of something that can get on rouge buffs leaving
that slight annoying scratch just when you thought you were done. The
800 compound cuts enough so that those simply don’t appear. Do be
careful with it, though. Too much, and crisp or millgrained edges or
fine beads and prongs can get decidely blurred. Finesse is the trick
here…
While there may be rings or other pieces that do indeed take a lot
of time, it’s usually because there are unforseen problems, like
porosity you find and then have to go back and burnish or otherwise
fix. Typically, most of the rings I polish can be brought to a mirror
finish in twenty or thirty minutes or less, starting from a raw
casting. These are cast rings in the line of my employer. Nothing
special in the castings. Sprues need to be cleaned up, sizes checked
and adjusted, rings stamped, details cleaned up, etc. About half the
time is the initial bench work. The rest at the polishing machine.
And again, these times are highly dependent on the tools and media
you use for the job. The 3m microfinishing films, their imperial
diamond sanding films, etc, and other micro graded abrasives make an
enormous difference in the amount of work you then have to do at the
buff. And there, those Japanese aluminum oxide platinum polishing
compounds from Gesswein are king. I’ve tried other competing
products, but have yet to find one I feel is totally their equal. If
I had, I’d have switched in a heartbeat, because those compounds are
quite costly. But the savings in time more than make up for the cost.
It used to be that to get a perfect polish on platinum you’d have to
go through a whole sequence of polishing papers all the way up to
about a 600 or 800 grit paper before you went to buffing compounds at
all. And often, it was necessary to burnish the surface too, even if
there were no porosity, in order to get a uniform enough surface
hardness that the old compounds like tripoli could give you a good
result. (It’s still needed if you find you have porosity to deal
with, but that’s another topic.) Done that way, it could easily take
an hour to finish a nice piece properly. But times have changed,
folks… It’s still not a quick few minutes. But it’s a lot easier
than it once was.
cheers
Peter Rowe
That’s a