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Crystal looking finish on 24K Gold


#1

We are new to this form of communication We find it very interesting
and educational. Are question has to do with 24kt and plat
jewelery.What process is used to form the crystal looking texture on
the gold while leaving the platinum untouched.

Thank You in advanced
Donnie Carl & EW Henneman
http://www.suttonplacejewelers.com/
Sutton Place Jewelers


#2

The crystal gold look is created by etching the piece in aqua regia
solution. You can see the process in the Sept. edition of AJM
magazine (pg. 80 there they use 18K). The one thing that many people
don’t tell you is that you really need to create a large crystal
structure in the gold for it to really look great. This normally
means that you have to heat treat it in a kiln. I made some cuff
links with this technique and it really did great. The only problem,
at first, was getting a consistent grain structure. The crystal in
the narrow areas anted to be a lot smaller than the crystals in the
more open spaces. I used 24 karat and it took a lot longer than 3 to
10 minutes to reveal the crystal structure well.

Without looking at my manufacturing notes I can’t tell you off the
top of my head what temps I used to get it even. I do believe it was
on the very high side of a normal annealing temp. I also let it stay
in the oven for quite a while to cool off.

Good luck, and keep in mind that this is not a wear resistant finish,
even in 18 Karat. It will scratch off easily and is not appropriate
for a wedding ring or other item that gets a lot of wear on a daily
basis. An exception is if the gold is so deeply etched that it
really creates a deep texture, not just reveals the crystal
structure.

Larry Seiger


#3
   Without looking at my manufacturing notes I can't tell you off
the top of my head what temps I used to get it even.  I do believe
it was on the very high side of a normal annealing temp. 

With 24K gold into platinum, I’ve generally used 1900 degrees F, for
two hours. You need an accurate method of controlling kiln temps,
though, to go this high. Using just a typical pyrometer, it would be
easy to accidentally be melting the gold again. On the other hand,
the real determinate of how coarse the crystals are, is how slowly
they form from the molten gold in the first place. So if you inlay
your metal just by melting it in, then actually heating the piece to
high enough so the gold was at least starting to melt again, then
turning it off so it could cool quite slowly, would give you really
nice coarse crystals. More uniform than just annealing high enough to
get grain growth. Another method that should also work is bimetallic
casting. Either way, remember to allow enough extra metal to
compensate for the horrendous shrinkage you’ll get with solidifying
24K gold, which can leave really spectacular sinkholes in an otherwise
smooth surface. These sinkholes or shrinkage areas, though if
cultivated and developed intentionally, can also be very dramatic,
since in these, the solidifying gold forms actual 3d relief crystals,
even before any etching. Coarse cubic system grains. Etch THAT, and
you’ve got something quite unusual.


#4

I used to get this crystal surface by electro stripping the object.
With different stripping solutions you will get a variety of different
looks. The bath I used was a cyanide bath and may not be available
today. This was very easy to achieve. Maybe Peter Rowe could comment.

Best Regards
Todd Hawkinson


#5

I too, did it occasionally on karat golds with electrostripping
baths. The aqua regia acid etch is more dangerous on items which are
mostly gold, including things like prongs, etc. The cyanide
electrostrip is uniform, and doesn’t attack the metal deeply into the
grain boundaries as much as an acid etch can do. But most
electrostripping baths are designed to be leveling, which means they
try to strip bright, not to a crystal finish. You can contaminate
the baths, use them at the wrong temps or wrong voltages, in order to
get them to misbehave and give you that crystal finish, which would
nave been considered a failure in terms of what the bath wanted to do.
The trouble is, these methods are highly dependent on the individual
alloys. Some 14K would give a wonderful crystal finish, and other
alloys would not. Many of the 18K alloys gave a good crystal finish,
but it was somehow dull, not reflective, and less than totally
attractive, when I used the various baths I could buy. Only my old,
depleted, (or in this case, saturated) baths, way too contaminated to
strip properly, seemed to give a good crystal finish, and then, only
sometimes, with some alloys. Just when I’d think I’d have it down to
a consistant process, I’d be asked to put that finish on some ring
only to find it was a slightly different alloy and didn’t treat
right…

Now I usually do this just on 24K into platinum. That, at least, I
can do consistantly.

Peter


#6

Is that crystal looking finish the same as mirror finish.? can
someone explain how to achieve this finish? with lap wheels?
maybe. thanks . marco