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Platinum joined with gold solder


#1

In a recent issue of AJM, Jurgen Maerz of Platinum Guild International
shows how to retip a platinum prong setting by attaching new platinum
tips with gold solder.

This provoked some questions on my part, and I sent him the following
email. Jurgen is apparently too preoccupied to reply at the moment,
so perhaps some Orchid members would like to comment on the issues.

Jurgen,

Your article on prong retipping with platinum in AJM caught my eye.

A technical question for you: in attaching the new platinum tip, the
cross section of the piece to be soldered on must be on the order of 1
mm x 1mm or so, perhaps a bit larger. What is the strength of the
bond between the gold solder and the two platinum sides that are
joined?

This generates a more general question: What is the nature of the
bond when platinum pieces are joined with gold solder?

I am thinking of the difference in melting points between the platinum
and gold here. With gold being joined to gold with gold solder, the
differential is relatively small, but with the platinum the
differential is very great. So I would imagine that in soldering
gold, there is some “wetting” of the pieces to be joined allowing at
least a small amount of interpenetration of molecules from both sides
at the join. But this wouldn’t be true with the platinum. Add to
that a very small cross section in the case of attaching a prong tip
of platinum with gold solder and aren’t you asking for trouble? Have
strength tests been made for this situation?

I appreciate your generosity with your expertise.

Thanks,
Riccardo Accurso
Ricco Gallery of Contemporary Art Jewelry
125 W German St /PO Box 883
Shepherdstown, WV 25443-0883


#2

Ricardo,

Had I received your e-mail, I would have been delighted to respond in
a timely matter. I pride myself in doing so. Even though I do travel
extensively, it is my job to answer technical questions and I always
do.

As far as the question at hand,using 14K wG to attach platinum tips
during re-tipping, let me say that it is my preferred method is to
use a laser and just re-build the prongs. If that is not possible, I
recommendto remove the stone and weld a new wire or tip to the head
and then re-set. If, however, the stones cannot be removed, I usually
prefer the gold solder method to attach tips to the prongs.

I have done this for many years and never! had a problem. I did ,
however, see many frosted diamonds in my time, where people tried to
tip using welding solders or even platinum solders, all of which are
past the burning point of the diamond in question.

To answer your question if there ever were any strenghts tests done,
I must say no, I have not. But a prong tip is usually not subject to
great stress other than wear. And you have seen that many times a ring
needs to be sized or a head attached to a semi-mount, where gold
solders are being successfully used. I think the many sucessful tips
speak for them selfes.The trick is not to create a cold joint, and the
tips will stay put. It is by far safer than doing it with higher
temperture material.

Hope that helps. If you have further questions, feel free to call me
at 949 760-8279

PLATINUM GUILD INTERNATIONAL USA
Jurgen J. Maerz
Director of technical Education
JA Certified Master Bench Jeweler


#3

Hello Riccardo!

When retipping platinum with any diamonds or gems in place there is
currently no alternative, but to use gold solder. I assume you
already know that. As far as stress tests, molecule differentials,
and other possible differences, I don’t see the value in the effort.
A great scientific effort to provide data proving the difference
between gold and platinum, is not going to help us here. The effort
would be to urge the metallurgy community to make a lower melting
solder containing platinum. The new soft platinum solder from
Precious Metals West melts at 2372 (1300oC) Fahrenheit. That is too
hot for diamond.

If your effort is to improve the quality of platinum repairs, etc.,
with diamonds in place, I suggest you contact Daniel Ballard at PMW.
Their website is www.preciousmetalswest.com. I would anticipate their
continued effort in platinum solder development. A lower melting
plat. solder for repairs near diamonds would of course be in great
demand, were it to be developed. My assumption is to reduce the
temperature to well below 2000 Fahrenheit, likely below 1800o so as
not to frost the facets of diamond. When adding platinum tips to a
diamond in a platinum setting I use 20 karat weld solder. This is the
highest karat white gold solder commercially available. The flow
temperature is 1610 Fahrenheit for the PM solder I am using now. It
does leave a difference in color and is softer than platinum, leaving
that unappealing indentation along the seam. With some careful
preparation and polishing it is hardly noticeable. As far as strength
and durability this 20k/platinum solder joint has never been a
problem for me. Good luck!

Tim


#4

Dear Ricardo, I am not as expert as Jurgen, but I have worked with
platinum for a little over forty years and do all my re-tips in
platinum where appropriate - which is most of the time.

It seems to me that you have already answered your question (What is
the nature of the bond when platinum pieces are joined with gold
solder?) There is a greater differential between the melting points of
gold solder on gold and gold solder on platinum, but in the case of
re-tips it simply does not matter as much as you would think.

Remember that we are talking about the tip of a claw, here. It’s not
as if we are going to subject this tiny tip to a Brinell test or
adhesion stress test. In normal circumstances our main concern is
simple abrasion through normal wear, and platinum will resist this
much better than any gold alloy. If, by some extraordinary
circumstance, the wearer of the re-tipped ring falls over and scrapes
the setting across concrete or down a brick wall, strength tests
become superfluous. It won’t matter whether the claw was gold or
platinum, it’s going to be destroyed.

You have correctly deduced that the solder join itself is a “weak
link”, but it’s not as weak as you might think. The adhesion of a
properly prepared and soldered re-tip is more than adequate for its
normal purpose and function.

I sometimes wonder if our increasing ability to technically
"diagnose" the minutiae of conventional practices does not cause us to
lose sight of the fact that most methods of working have been tried
and found true for all normal purposes. If sound bench practice is
applied to the work at hand, the technical aspects of its completion
and durability will be as satisfactory as the very nature of the
materials we use will allow.

This is not to say that we shouldn’t bother asking questions like
this. It’s a good question and I hope the above has helped. Kind
regards, Rex from Oz.


#5
   This provoked some questions on my part, and I sent him the
following email.  Jurgen is apparently too preoccupied to reply at
the moment, so perhaps some Orchid members would like to comment on
the issues. 

Riccardo, your question to Jurgen pretty much summed up the state of
affairs. In fact, there’s yet another potential source of trouble, and
that is the fact that the coefficients of thermal expansion (COE)
differ between gold alloys nd (including solders) and platinum. so
joints made with gold solder to affix platinum parts are already
slightly strained once they cool. As you note, there is little
penetration of the platinum by the gold solder, so that though the
platinum is “wetted” by the gold solder, it’s not penetrated much, if
at all. The result is generally a bond which, if stressed a lot, will
fail more quickly than the same bond made between gold parts with the
same solder, or platinum parts made with platinum solder.

But it’s not quite as “cut and dry” as that. Consider the
traditional platinum solders too. While the highest melting of them
do approach platinum’s melting point, and contain some platinum, the
lower, safer grades, are mostly palladium and silver, and melt enough
below the melting point of platinum that they too, don’t give a good
penetrating bond. Try soldering some platinum wires to a platinum
part with 1100 solder, then try pulling them off again with a pair of
pliers. You’ll be surprised at how easy it can be to just peel off
the wires. The higher melting platinum solders do a lot better, and
the new, plumb platinum solders, despite their relatively safe melting
points, also seem to give much stronger joints.

But when we’re retipping prongs on diamonds, not to mention other
gems which can withstand even less heat than diamonds, we’ve got a
major problem. Diamonds simply cannot withstand the heat needed to
use even the easiest melting of the platinum solders without major
risk of burning the stone. while I’ve now and then used 1100 or even
1300 solder grades to solder fairly close to a diamond (melee. I
don’t risk this with bigger stones), and sometimes can get away with
doing so as close as a millimeter or two from the stones if I get in
and back out real quick, with lots of boric acid on the stone, it’s a
big risk, and I burn some stones doing this. The resulting repairs
may be better than if I’d done them with gold solders, but I also end
up having to replace burned melee about a third of the time. Were I
trying this with actual retipping tasks, I doubt I’d get away with it
at all, ever.

So IF you’re going to be retipping the diamonds in platinum prongs,
you’ve simply got no choice but to use gold solders, simply to get
within a safe melting point of solder. Yes, it’s not as strong a
joint as one would like. But platinum is malleable, wear resistant,
and strong stuff. If you’ve prepared the joint well (the existing
prong surface is flat and clean, and well fitted to the added piece,
you’ll find that though the joint may not be optimal, it will hold up
well enough. In fact, putting platinum tips onto gold heads when
retipping holds up better than putting gold tips on, simply because
the new tips in platinum will wear so much better than new gold tips,
even if the solder joints holding them on are less strong. Of course,
in doing this, the different metal on the tips is visible. But
usually not objectionable visually.

The conclusions to draw are several. You can retip platinum prongs
using platinum soldered on with gold solder, if this is the proper
repair to be making at all. Doing so is actually standard practice
much of the time. But it will be a superior repair if you can unset
the diamond, retip, or better, rePRONG it, not retip it, using all
platinum metal and solder both. Or use a new head entirely.

And of course, if you happen to have a piece that really needs
retipping and cannot be repronged, yet you’re not comfortable with
adulterating the piece with gold solder, you’ve now got an option that
didn’t exist until a few years ago. Laser welders can safely fuse new
platinum onto a platinum head, even with relatively heat sensative
stones, like emerald. I’ve seen successful retippings in platinum
done even with Opals (!) using lasers. If you don’t have a laser
yourself, you can always opt to send the work to a shop that does
have one. There are several firms which now offer that service. It
does cost more, but if the jewelry is worth it, then the resulting
repair can be far superior.

Hope this helps.
Peter Rowe


#6

Hello: Reading through your messages, I can see you have resolved many
things we still have to make them by hand. There are not many
commercial products specially developed for jewelry, the few we can
find are all imported from Italy, Germany and USA. We can buy tons of
tools and recent technology machines, but nothing like chemistry
products or the different alloys used in solders and for melting
purposes.

In my twenty five years working in jewelry I have always made my own
solders, using different alloys and testing what other people told
me. Each one has its specific use, but the more simple formula seems
to be the most effective.

I have logged some formulas for platinum you can evaluate, test or
log for simple reference. From the higher to lower melting point they
are (expressed in parts):

Nr. Platinum Gold Silver Palladium
1 900 100 - -
2 620 - 230 150
3 333 334 333 -
4 333 - 667 -
5 270 - 730 -
6 - 750 - 250
7 - 625 190 185
8 - 500 380 120

I have tried 3, 4 and 5 with good results, but their melting point
are around 1200 C. Too high for the case on discussion, and may the
gold solder be a great solution when a lower melting point is needed. I
have used natural gas and oxygen. Also a rhodium bath to hide a
yellowish mark. The rhodium plating is very strong and lasts too long.

I have logged others solder alloys formulas used for gold, white gold
and silver. If someone think it would be of some interest, I can write
them down.

Regards,
Daniel Mischelejis


#7
   In my twenty five years working in jewelry I have always made my
own solders, using different alloys and testing what other people
told me. Each one has its specific use, but the more simple formula
seems to be the most effective. 

Daniel,

this is off topic but you’ve brought up something I have just started
doing research on. Perhaps you can help me. I have recently been
frustrated with the lack of appropriate solders for 18 K palladium
white gold. I have made some of my own solder as well but I’m having
trouble finding as to the proper alloy needed to make a
solder specifically for 18 karat palladium white gold. The color
difference is the main problem, but there is also a problem with the
nickel solders polishing out faster than the gold leaving seams. I’d
like to get extra hard, hard, medium and easy alloy mixes since I do
so much faabricating, but anything would be better than using the
solders available commercially now for nickel. Do you have any
on palladium white gold solder alloys?

Thanks for the help
Larry Seiger


#8

Riccardo: The point that you’ve raised is a valid one. Gold solder
will hold platinum tips on a platinum prong very much like a good
glue bond (and everyone knows how much I love glue!). Retipping in
this manner will work if the bond was clean and the solder flowed
properly. And there’s the catch…all of the retipping failures that
I’ve seen, platinum or gold, have been due to improper soldering.
Anyone who has worked with white gold knows how it loves to oxidize,
and so often prong tips are soldered on with a hot, oxidizing flame
without adequate preparation to the prong beneath the tip. Platinum
will encourage us to apply more heat than necessary, causing us to
overheat the solder and destroy the bond. I’m a firm believer in
removing the stones before retipping, unless you are forced to do
otherwise. Sure, I charge a little more for my repairs, but I never
have to worry about the job coming back or frying a stone. Modern
gem enhancements often make stones very vulnerable to the heat of the
torch. Of course, gold solder will not make an acceptable bond for
sizing. It will likely fail under stress. So, for all of you out
there who are just starting to work with this wonderful metal…learn
to weld.

Happy bonding!
Doug Zaruba


#9

Larry: I’ve been using the lower temperature platinum solders, since
they are basically palladium and silver. Works great. I use Hoover
& Strong solders, but I’m sure there are others. I’ve been hearing
great things about PM West solders, but haven’t tried them yet. I
like the 1300 solder, but it can be close to the melting point of the
gold. Let me know what you find. I’m always looking for a better
way…

Doug Zaruba


#10

Apparently my questions in the original post were not phrased as
clearly as they might have been.

What I was attempting to get from Jurgen, and the others on the list,
is an in-depth analysis of the nature of the bond when using gold to
join platinum. And by extension, the nature of any soldered joint.

This is a deceptively simple question, but like many other questions
of this sort, the answers can be quite complex once the details are
examined.

Peter Rowe picked up some of the major points: bonding platinum with
gold is inherently weaker than bonding gold with gold because of the
greater difference in melting points of those metals, and he adds,
correctly, that the bond is further challenged with stresses
introduced by different expansion coefficients between gold and
platinum.

Perhaps Peter, and maybe some of the other really knowledgeable metals
people (James Binion, Martin in Denmark, John Burgess, among others)
can discuss what happens in detail when soldering takes place.

The Mertens have a point about “most methods of working have been
tried and found true for all normal purposes”, but if we settle for
just that much, there may be a lot that we will never discover and
learn. There is a place for practice and a place for theory. Either
one without the other is like walking with one leg.

I know you can “get away with” soldering the platinum prongs with gold
solder. People do it all the time. But if you do it blindly,
assuming that it is a totally adequate method, you may be in for a
surprise when that customer comes back and asks you about the retip
job you did and his missing 2 carat diamond that came out when one of
the tips failed. Impossible you say? Don’t be so sure. Yes, the
prong has a claw shape all right. How about the claw catching on
something and pulling sideways? Impossible you say? Famous last
words.

Ricco Gallery
125 W German St/PO Box 883
Shepherdstown WV 25443


#11

Hello Larry: The main problem with solders is always the color
difference, as gold changes its color easily depending on the
components of the alloy. To minimize this problem the solder must be
made with the same alloy of the gold used in the jewel. In my solders I
introduce brass (zinc + copper) and cadmium in order to lower the
melting point. To make 18 karat palladium white gold solder I only use
cadmium to lower the melting point trying to get the minimum color
change.

For a general purpose white solder I prepare 100 grams as follows:

Fine Gold: 75 grams Your White gold alloy: 10 grams Silver: 12 grams
Cadmium: 3 grams

Cadmium must always be added as the last component while you are
melting the alloy. It fuses at 321 and boils at 767 Celsius degrees.
When all the other components are melted, you must move the flame
away from the crucible, let it get cold for ten seconds and then throw
the cadmium into the crucible. It will fume for one second or two. Mix
with a stick of graphite to homogenize the alloy. Now you can apply
the flame again for only raise the temperature enough to emptying the
crucible. I am sorry if you already know this.

Always consider the use of a rhodium plating when a mismatch color
exists after polish. We use rhodium plating although there are not any
weldings, because it makes white gold more shining and whiter.

I do not use alloys with nickel. Nickel turns gold brittle. I have
read some articles against nickel because of allergic effects in some
people.

I hope this can help you, Best regards.

Daniel Mischelejis Buenos Aires, Argentina