Being a small town jeweler I don’t get to work on platinum as much
as I would like to, but I do have some experience with it. I would
always make sure to use separate files and buffs with platinum. The
problems with using the same buffs and files come when you start to
weld on platinum. I’m by no means a metallurgist, but am pretty sure
small shavings of gold or silver from your file or buff will embed
in the platinum and then contaminate and ruin the area where you are
welding at. I’m sure there might be other reasons, but this is all I
know. So yes, definately have files, buffs, and other abrasives set
aside for platinum only.
If anyone can explain what evil it is that we are supposed to be avoiding by using different equipment for finishing platinum, I am eager to be enlightened.
Well, at the bench, it includes files, which can get bits of
platinum or gold stuck in the teeth to contaminate other metals,
though frankly, like you, I don’t usually differentiate as much as
sources suggest I should, and have never had major problems with the
piece as a result. But I pay the price for that when it comes time to
refine my scrap, which then is also not totally isolated gold from
platinum. At the polishing wheel, though, I’ve not had problems. I’d
note that I use Gesswein’s platinum polishing compounds for much of
my gold work as well. But I’ll also note that those are aggresive
compounds, and harsh enough to affect soft stones, especially
facetted ones. So when I need to polish around a softer stone, or a
very soft metal, I’ll use buffs that have NOT been used for platinum
compounds. A rouge buff with only red rouge on it will give a
slightly higher finish to gold, and especially silver, than it would
if it had platinum rouge on it. But the difference is slight. On the
other hand, a rouge buff using traditional rouge will leave most
facetted stones with nice clean sharp crisp facets. Buffing that same
setting with platinum rouge will leave all those facet junctions just
slightly rounded over. Not a nice thing to do to a nice stone. The
quandry, of course, comes when one is polishing a platinum setting
that’s holding one of those soft stones… That’s one of the times
when the value of fully prepolishing a piece and a setting before
setting the stones becomes fully apparent.
Peter Rowe
Hi Steven;
Contamination of platinum is a problem in this regard: Platinum,
especially if it’s cast, tends to be slightly porous on the surface
unless it has been worked to compact the surface, so gold, silver,
and other alloys in buffs get picked up by this surface. Same
contamination can happen from files (which are always shedding tiny
bits of steel), and from abrasives contaminated with other metals.
Also, platinum, because it is so soft and dense, tends to grab other
metals, as if it were sticky, so it can pick up steel from rolling
mills and hammers. Although these are minute quantities, further
planishing and rolling can drive the into the surface, and further
hammering and milling add more. Cleaning in nitric acid removes a
lot of it, especially the iron or steel, which is the most
problematic because it oxidizes before it melts and alloys with the
platinum.
When you weld platinum or even use the higher temperatures of
platinum solders, it’s well above the melting point of the other
metals. In fact, many of them start to vaporize at those
temperatures. This is bound to leave pits in your solder seams or
welds which can only be removed by cutting out the offending areas.
Also (and I speak from personal experience), when those metals have
melted into the weld, (as would lead in a gold solder seam) as you
get up to the flow temperature of the weld, they vaporize and the
molten platinum makes a small explosion and sprays tiny, really hot
bits of molten platinum, usually spitting them right in your face. It
makes quite a “pop” as these gasifying metals try to escape the melt.
Scares the heck out of store managers too as it blows away a section
of the ring shank you’ve been soldering.
I also tend to not bother with separate tools for platinum, since I
don’t do nearly as much work in it than I do in gold. I rely on
frequent cleaning with ultrasonic and pickling in nitric. And when
I’m ready to weld or solder it, I take a lot of care to get it clean,
since it’s a costly metal in the first place, but especially when you
have to give the refiner his share after you’ve contaminated it. One
day I’ll be more disciplined and do it the right way, but like you,
I’ve been getting away with being a tad sloppy.
David L. Huffman
Hello Laura and others;
The original post was a question about polishing platinum. Let me
try to shed some light on this.
First, the issue of using separate buffs for platinum is or isn’t
relevant. Here’s why. If you are going to solder platinum after
you’ve been buffing it, you need to clean it thoroughly in any case.
If all you’ve ever polished with a buff is platinum, then the problem
is only about getting the polishing compounds off before you heat it.
If you’ve used that buff for other metals, you especially need to get
it clean. Other metals trapped in the surface of your platinum will
create problems for soldering, causing pits, brittleness, and small
explosions (no kidding). But if you’re done with a piece and are
ready to put the final polish on it, it won’t matter that the buff
has seen other metals. Again, buffs reserved for platinum only are
the best practice, but not that critical. Cleanliness before
soldering, as in pickling in strong nitric acid, is pretty
important.
Now about polishing.
The best reason for buffs that are used exclusively for platinum is
to avoid contaminating the buffs with the wrong compounds. If you use
two different grades of polishing compound on a single buff, from the
point at which you charge the buff with the courser of the two
compounds, that is how course the cutting/polishing action will
always be on that buff unless you completely clean the buff (messy
work).
Platinum is dense and soft, it hangs on tools like files and
gravers. Now polishing is really a matter of making smaller and
smaller scratches until they are so close together light sort of
bounces off the surface rather than lighting the topography of these
scratches. But unlike 14K gold, which can be cut down pretty quickly
as in file, then 320 grit, then tripoli on a felt lap, then rouge,
platinum has to be led by the nose through a few extra steps. The
surface smears, rather than cuts. Same happens with high karat golds,
to a degree. Silver is somewhere in the middle. So you need to use
several consecutively finer grades of abrasives when you sand, and
likewise, more grades of polishing compounds when you polish. With
platinum, you’ll find that it’s a lot of work to remove file marks
with 320 grit paper, and just as much work to jump from that to 600.
So after the filing, a little 280, then 320, then 400 (or 600 with
more elbow grease), then ideally, a 2/0 grade of crocus or some
equivalent to an 800 grit will work better, and you’ll need to watch
that each finer grade removes all the scratches from the previous
grit. Some people prefer to burnish after 600, but it takes a fine
touch and a good carbide burnisher for this to be any advantage,
since you can chew up the surface with the burnisher while making
nice little shiny streaks. I sometimes burnish between the 320 and
the 400, just to pack down the surface of cast pieces (which tend to
be slightly porous).
After the waltz of the sand papers, you’ll need to do somewhat the
same with abrasives. Here’s the cheapskate goldsmiths route:
something a bit courser than tripoli, like gray star or one of the
"platinum pre-polish" compounds will get you from the 800 or 2/0 grit
to the tripoli, but without that, it’s tough to get the tripoli to
cut out the scratches, fine as they are. Then tripoli, then rouge,
preferably a yellow or green compound. I usually use a felt lap for
the first two grades, then “read” it with a once over on a buff of
the same grit, making sure I get all the scratches but not leaning
on it enough to round off corners (as if this is much of a problem
with platinum). No lapping with the final polish, just bring up the
luster on a buff.
But the best solution is to get a set of at least 3 grades of
polishing compound (some people like 4 grades!) that are especially
formulated for platinum. These are a bit pricey compared to the other
stuff. There’s are pre-tripoli types, then some that are similar to
tripoli in grade, then some that are between what you’d get with
tripoli and what rouge would do, then the final luster compound. Most
jewelry suppliers have compounds for platinum, and they are getting
more reasonably priced (they used to be sold by the gram!). This way
you’ll get optimum results, and even with all the extra steps, it’s
actually easier, because here’s another thing about platinum: it gets
really hot to hold when you’re polishing, especially lapping. More
graded steps in the process mean less bearing down on the buff or
lap, hence, less burned fingertips. And finally, if you believe the
advertising, you can do all of this with a selection of rubber or
silicone wheels and a foredom handpiece. Depends on the piece mostly,
the shape of the surfaces, etc. Just expect to use at least 3 grades
of abrasive between 800 grit and a final polish.
Platinum, the metal a jeweler loves to hate. It’s both finicky and
forgiving, it’s expensive to the point of vulgar, but it sells
itself because it is such a tasteful choice, it’s heft is
unmistakable, almost alien, yet with patience, it can be transformed
into something as delicate as a butterfly, and it
lasts…incorruptible. (Ok, platinum guild, you want to buy any of
that plugging?).
David L. Huffman
The polishing “mops” are not to be sneezed at. KEEP THOSE POLISHING
WHEELS SPERATE from the gold cloth wheels. You must not contaminate
the gold to platinum items, or you will run into problems. Its like
polishing silver to steel. The mixed compounds will ruin the delicate
polishing effects. Platinum is a totally different game. I have seen
a ring polisher spend 1/2 hour attempting to make a ring shine (as
you call it). You can’t make a platinum ring just shine. Its hard
work to bring up the luster, separate compounds, wheels, brushes, all
being kept separate AT ALL TIMES, Steam cleaning with a soni-cleaner
in between the many polishing stages.
AGAIN, THOU SHALT NO MIX THE TWO TOGETHER. “Gemz 1:1–1:2”…Gerry
Lewy!