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Platinum coated diamonds


#1

Through a series of tragic errors I was forced to weld a shank very
close to some 1 pt. diamonds.

I opted to heatsink the stones rather than remove them on the off
chance that the worst wouldn’t happen, but it did. They’re only 1
pointers and the my cost of 'em is zero dollars so there’s only the
labor, (and had I removed them first…)

Anyway, I was told by someone that I could use hydrofluoric acid to
remove the coating that results from some magical fuming from
platinum. (I use LP and a niobium stick, etc. I haven’t the luxury of
a separate platinum room, but I take precautions as best I can.) I
found reagent grade hydrofluoric acid at a local chemical supply
house for close to $50.00 a pound, but the guy I work with & rent
from won’t allow it kept in his building. I think he thinks it’ll
cause a sort of “China syndrome” and kill everyone in the building
via osmosis or something.

I know it’s extremely dangerous and am loath to work with it, but
I’m not keen on unsetting these stones because if the tiny prongs
(bright-cut) snap off, there are even larger diamonds next to the 1
pointers…

So I will try the acid.

Do any of you have any experience using this acid for this purpose?
What about using it to clean off merely overheated/burned (not
involving platinum) diamonds?

And aside from the usual precautions, i.e., rubber gloves, apron,
and a face shield & ventilation, and some sodium bicarbonate handy,
are there other tips or precautions you can offer.

Thanx!
Doc


#2

Hi Doc;

I’m half joking, but only half. You worry me. Last time, you were
looking for asbestos. You don’t have some sort of death wish, do you?
I can’t blame your landlord. Hydroflouric can certainly kill, and it
doesn’t take much to do major tissue damage. Didn’t you read the
Orchid posts on it? One guy said he spilled a single drop on his
finger and the nail fell off the next day.

Aside from that, if you’ve toasted the diamonds, there is no topical
application that’s going to fix that. If they’re frosted, it’s
because the surface is burnt. Nothing short of polishing will fix it,
and that’s not really an option for 1 pointers. I’m afraid you’re
going to have to bite the bullet and pull them. Someone with a laser
can replace any beads that break off. I’d advise against soldering to
re-tip. Platinum, being a heat sink, will make it likely that you’ll
burn more diamonds before you get a solder bead to stick, or else the
solder will just flow all over where you don’t want it. It can be
done, but it’s a challenge. Best of luck.

David L. Huffman


#3

This happened the other day. I was called on a Thursday to size a
platinum ring which had pave.01 pts set in the shank with no holes
drilled from the back.Oh yeah this held a Round 10ct. Solitare and
he was flying this ring to his customer the next morning. This ring
was being sized down and I knew regardless of how much of a heat
sink I put on the shank,I was going to smoke some Diamonds. I was in
a situation that it had to be done right now.

I had called and said to him that this was going to happen .I had to
use seamless 1700 solder. This was a $200,000.00 Dollar ring. Well
after replacing 18 Diamonds he flew the ring to his customer and
they loved it.

No I do not have a Laser yet. After doing this job I really needed to
see a Therapist. I was totally stressed.

Memo to self, get Laser. Doc replace Diamonds

Johneric


#4

Doc, just what did you do? If you laser welded or PUK welded the
shank, and are now faced with “smoke” from the welding (black fumes
deposited on the diamonds, but the diamonds are OK underneath this),
then you need not go so far. Heavily coat the diamonds with ordinary
boric acid firecoat first, then more soldering flux (Batterns works
fine, or any of the paste fluxes.) Then gently heat until the flux
liquifies. Heat to “just-barely-glowing-in-a-dark-room” sort of
temperature. The flux will lift off that metal vapor that condensed
on the diamonds.

If, on the other hand, you torch welded the platinum, and the
diamonds did not get coated with metal condensate, but instead, got
hot enough to burn the surfaces (and now look white and frosty,
instead of blackened), then you too are cooked, figuratively. Acid
won’t restore the polish to the diamonds. You’ll have to replace
them. By the way, if that’s the case, and you have trouble with the
bead set prongs, someone with a laser welder or PUK welder can
easily restore them without damage to the diamonds.

Oh, and HF won’t dissolve a platinum vapor film very well either. It
dissolves silica just fine, and does a number on your lungs, and all
that stuff. But it won’t much help your cooked diamonds, if indeed
they are heat damaged. If only coated, then HF is more than you need,
and dangerous stuff too.

Peter


#5

I have burned a couple of melee when platinum soldering close to
them, but have never seen them “coated”: they appeared frosted, but
were actually pitted. A wedding band rep, that did a lot of platinum
and diamond bands, told me they used to have to allow for a small
percentage of this sort of damage when having to size some of their
rings with the torch, but after going to the laser this problem was
eliminated. Now that I own the laser I never take a torch to
platinum, and it’s even possible to retip in platinum without
removing the stone.


#6

If the coating is only a few atoms thick (as with a flashed vapour
deposit) wouldn’t it be safer to use a Q-tip type applicator dipped
in aqua-regae(sp?)?

This way the acid wouldn’t get some where it shouldn’t, but there
should be more than enough to remove the small amount of metal
required.

Hydrofluoric acid is about as nasty as acid gets, you should invest
in gloves (gauntlets?) that are rated for this acid as the effects of
it on the human body ain’t nice…

Cheers, Thomas.
Janstrom Designs.


#7

Doc,

Don’t do it. 1st, that acid is nasty stuff. 2nd, won’t work anyways.

once a diamond is burnt the only way to remove it is to re-polish
every facet.

Roger D. Flanders
Diamond cutter


#8

Since your shop mate won’t let you keep the stuff in the shop, I
suggest setting up a small area right next to the emergency room of
your local hospital to do this.

Besides, it won’t work. The actual surface of the diamonds have been
burnt, not coated. Even if the diamonds were coated with platinum,
how is the acid supposed to etch platinum off the diamonds without
also etching the platinum ring itself?

The only way to make the diamonds look right is to re-polish them,
which will require taking them out. just replace them and file this
job in the lessons learned category.

Larry


#9

Doc -, i suppose you missed my comments about PM wests’ palladium
white gold solder on platinum jewelry if you had used PM west’s PD
white solder you wouldnt have this problem .

if you must experiment i would try the HF acid by doing it outside
and position myself upwind when the nieghbors are not at home,
although if the fumes draft through an open window of thier house it
might melt the fur off thier cat the thought of which doesnt really
bother me as a furrless cat doesnt tend to successfully murder wild
song birds for fun anyhow.

my experience is the surface of the diamonds can only be restored by
polishing if the diamonds are less than .50 cts you are better off
taking your lumps and crack or break them out of the setting so as to
save what is left off worn out prongs and then replace the diamonds
you can save the bits for the folks who use them for sand paper. by
the time you use a bunch of time spend money and have untold worries
you could have been better off just getting back to work. i know !
ive’got my well worn t shirt !

goo


#10

Don’t take this the wrong way but please return the hydrofluoric
acid to the store where you bought it. You don’t have the training or
equipment to work with it if you are asking these questions.

It is not only hazardous from the standpoint of getting burned but
it is anesthetic so you will not realize that you have it on you. It
will kill you if you spill enough to cover 5% of your skin area and
there is virtually no way to keep this from occurring if you do
happen to spill that much.

Don’t use it,

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#11

Hi Doc,

I don’t know about the acid, but the diamonds shouldn’t be too hard
to remove and replace. I assume you’re saying they’re bead set. Use
a broken off tiny ball bur or other bur with a shank that comes to a
fine diameter at the top. Put the ring upside down on your wooden
bench pin and slowly use a hammer and the broken bur to tap out the
diamond from underneath. (Make sure you’re tapping it out over a
depression in the bench pin so it has room to come out.) Platinum
beads should bend easily and not break off. Set a new diamond in by
using a beading tool to gently push the beads back down over it.

Lauren


#12
Hydrofluoric acid is about as nasty as acid gets, you should
invest in gloves (gauntlets?) that are rated for this acid as the
effects of it on the human body ain't nice..... 

If anyone is entertaining the idea to work with hydrofluoric acid,
than it is important to understand that risks involved, are not usual
risks of handling acids.

Hydrofluoric acid formulae is HF. When it contact the skin, Hydrogen
splits from Fluorine. Hydrogen ion in free form is a strong acid by
itself and can do a number on tissue, but the real danger is free
Fluorine. It can penetrate into the tissues very quickly and very
deeply destroying everything on its path, until it encounter Calcium.

( Fluorine eagerly combines with Calcium and it’s salts. That is
exactly why it is used in toothpaste. Reaction is 2F + Ca = CaF2.)

When Fluorine combines with Calcium on cellular level, the cells
containing Calcium die. Medical term is “tissue necrosis”.

If you have to use it, never use it alone and know how what to do in
case of accidental exposure.

Leonid Surpin
www.studioarete.com


#13

I’ve not used hydrofluoric acid to clean diamonds, however I
regularly use an alternative for general glass etching. This is
ammonium bifluoride crystals, which are considerably safer to
handle, dissolved in water to make a strong solution, to which I
then add strong (say 20%) sulphuric acid. I use a plastic container
for the mix.

To a certain extent the sulphuric acid is optional, since the
ammonium bifluoride alone dissociates in water to give ammonium
fluoride and hydrofluoric acid.

The resulting solution will contain enough hydrofluoric acid to
satisfy most glass / glaze etching as well as some metal pickling
requirements, and without the need to cope with the dangers of a
bottle of 70% hydrofluoric acid on the premises.

It is also considerably safer to transport, store and dispense the
solid ammonium bifluoride than liquid hydrofluoric acid solution.

Paul Jelley
London UK


#14

Hello, I have refered all the literature we have at the college
platinum is not affected by hydrflouric acid. It dissolves in
aquaregia. you may try removing the coating on the diamonds by
applying aquaregia selectively on the coated diamonds. you would have
to do it under a fume cupboard or a well ventilated area.

Best regards,
Umesh


#15

Blackening of Diamonds after De-Stoning process in Aqua Regia
August 1, 2018
Q. Dear Sir’s
I introduce myself as Prakash V Pai from India.
I work as a senior manager, Castings in a firm which manufactures Gold & Studded jewelry for Exports.
Our Exports consists of 75-80 Studded jewelry. Recently one of the orders were cancelled by a customer who had ordered studded rose gold rings. The cancellation was done when the cast pieces were in QC stage. Due to this, we rejected the entire production.
To de-stone the jewelry and to recover the gold, I had to process the rings in Aqua Regia acid which we normally do without any problems, but this time the stones changed color and turned from white to blackish.
I tried boiling the stones in order to recover the original color by doing the following process:

  1. Re-boiled the diamonds in Aqua Regia.
  2. Boiling the diamonds in Perchloric Acid
  3. Kept the Diamonds in Cyanide solution
  4. Boiled the diamonds in Hydrochloric Acid
    All the above processes did not yield any results and the diamonds had a shade of black with it.
    Can somebody please explain and shed some light, as to what was the cause of diamond turning black?
    How to clean it again to bring back its original whiteness? What are the chemicals I need to use?
    Re Cutting & Re Polishing on lathe again of diamonds means loss … Please Help!!
    Eagerly awaiting for your reply…
    Warm Regards,
    PRAKASH PAI
    Shop Employee cum Hobbyist - MUMBAI MAHARASHTRA, INDIA

#16

For those of you who would like to avoid any more problems like this I have a laser and I do work for the trade.
John Wade Wade Designs
3590 Woodbrook Drive Rocky Mount NC 27804
252-451-9270