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Fusing 24K gold onto silver


#1

First, I just want to say that I do all my fusing with 28g & 30g, so
"too thin" isn’t the issue. Also, if you can avoid putting the torch
on the back-- which should be on a natural, not compressed,
charcoal block-- it is best, because the backing sheet will then
remain formable, not stiff and brittle.

Now my problem-- I live fusing 24k gold onto my fused silver. It
works just fine, except that the silver tends to melt over the
surface of the gold and hide it. This is particularly a problem with
granules. Even after I clean them off (no longer so round), they
don’t look like 24k any more. Any suggestions? Thanks ever so!

–Noel


#2

You are obviously better at this than I am Noel (I’ve only begun to
fuse different metals), but had you thought about putting yellow
ochre over the gold to keep the silver off?

Tom


#3

If you are fusing the 24K to the surface of silver, you are most
likely (I would think, anyway) actually alloying the 2 metals
together a bit, at least if the silver is covering the gold surface.
The visible part, then, would no longer be 24K. Just a thought,
anyway.


#4

Silver dissolves in dilute nitric acid - will not
touch any gold alloy, and certainly not 24k…


#5
    Now _my_ problem-- I live fusing 24k gold onto my fused
silver. It works just fine, except that the silver tends to melt
over the surface of the gold and hide it. This is particularly a
problem with granules. 

Noel, this sounds as if it’s a problem with the bonding. Ask
yourself if you have enough copper coating on the gold granules to
lower the fusing temperature? Silver melts at a lower temperature
than gold, so it’s really easy to get your granules coated with
silver. Keep your torch concentrated more towards the silver, so the
silver is only attaching to the bottom of the gold granules, rather
than getting the gold granules hot enough the silver runs up them and
coats them. Are you using a liquid flux and is it thinned out with
enough water to keep it from “working” too much, thus lifting the
granules and preventing their fusion before the flux becomes molten?

    Even after I clean them off (no longer so round), they don't
look like 24k any more. 

Several things can be possibly tied into this and your fusion
problem. The first is the gold itself. Quite a few manufacturers will
use just a bit of zinc (it vaporizes) even in pure gold or silver,
because, so I’ve been told, it makes the wire easier to draw and
sheet easier to roll. This same source also said it causes a problem
in fusing, with the trace amounts of zinc causing microscopic pitting
and preventing the fusion. So you might check with your manufacturer,
and tell them your reason for the inquiry. A reliable source in the
U.S. is Hoover and Strong.

Another problem is that 24 kt. gold is very soft and can be easily
distorted with just the slightest pressure. You may want to change to
22 kt., as the difference in color is hardly perceptible, but it has
the ability to withstand a little more. I’ve also found the 3M
bristle disks in the 6 and 1 micron size are great for putting on a
very nice polish without flatspotting. A quick touch with rouge on a
loose muslin wheel completes the final polish.

I hope this gives you some ideas to pursue, and changes your
frustration to pleasure in achieving what you envision.


#6
 I've also found the 3M bristle disks in the 6 and 1 micron size
are great for putting on a very nice polish without flatspotting. 

Hi Katherine. Where do you get the 3M bristle disks in 6 and 1
micron sizes? Are they available separately in the smaller (1 inch
or less) diameters? I haven’t seen them except in sets.

Thanks.
Pam Chott
Song of the Phoenix


#7

Katherine, If there is zinc added then it is not 24k no ifs, ands or
buts. So if it has zinc in it it is not pure. Zinc is mostly added
to lower karat gold alloys where it acts as a de-oxidizer . It is
not normally added to silver although some de ox sterling alloys
have some present.

Jim


#8
           Katherine, If there is zinc added then it is not 24k no
ifs, ands or buts. So if it has zinc in it it is not pure.  Zinc
is mostly added to lower karat gold alloys where it acts as a
de-oxidizer . It is not normally added to silver although some de
ox sterling alloys have some present. Jim 

Well, theoretically. but Jim, remember that some bright folks have
remembered that 24K isn’t always 24K. it’s not just a definition of
pure gold, it’s a legal term, and as such, in labeling gold, has a
tolerance specification. Alloys can, and are, made, to be pure enough
so one can mark it 24K, yet it still has a tiny fraction of alloying
metal designed to materially alter the alloy. These so-called micro
alloys have the look of 24K, but once heat treated correctly end up
with a hardness and durability more like 18K. I don’t remember for
sure the alloying agen, though I seem to remember titanium as the
alloy. Anyone know? I’m pretty sure it isn’t zinc, but who knows.
Whatever it is, just a trace is apparently enough to greatly alter the
alloy’s properties without bringing the purity down too low to
legally mark 24K.

Peter


#9
    Hi Katherine.  Where do you get the 3M bristle disks in 6 and
1 micron sizes?  Are they available separately in the smaller (1
inch or less) diameters?  I haven't seen them except in sets. 

1", 3/4" and 1/2" available from Rio Grande and some dental
suppliers, in packages of 12 for each size and grade.


#10
    These so-called micro alloys have the look of 24K, but once
heat treated correctly end up with a hardness and durability more
like 18K.  I don't remember for sure the alloying agen, though I
seem to remember titanium as the alloy. Anyone know?  I'm pretty
sure it isn't  zinc, but who knows. Whatever it is, just a trace is
apparently enough to greatly alter the alloy's properties without
bringing the purity down too low to legally mark 24K. 

Hi Peter! I use a product called PureGold that is .9985 pure and it
is alloyed with the rare earth element-Gadolinium. It’s mineral 64 on
the element charts and named for Gadolin, a Finnish chemist. The rare
earth metal is obtained from the mineral gadolinite.

I use it in wire form to weave with but have also cast it for bezel
caps. Its seems easy enough to cast but should be gated properly and
not allowed to overheat in the crucible. The heat treating is a
simple heat soak for 3 hours at 482F. (I used to do it in my home
oven!!)

My source for this material is John Bernardin of PureGold at
510-262-9560.

T Lee T Lee Fine Designer Jewelry 18 University Ave NE Minneapolis, MN

55413 Snow is gone…so sad, time to wax the board and put it away…


#11
        Well, theoretically.  but Jim, remember that some bright
folks have remembered that 24K isn't always 24K.  it's not just a
definition of pure gold, it's a legal term, and as such, in
labeling gold, has a tolerance specification. 

Yes I know that Peter in the US the spec will allow a micro alloy
of .0015 which is the PureGold99 gold calcium alloy. but I have
never heard of adding zinc as a micro alloy. It is very difficult to
control alloy percentages in the .001 range during manufacturing and
the legal limits for purity are very strict. The PureGold99 alloy
must be melted in a inert atmosphere because calcium is very reactive
with oxygen just like zinc and would oxidize right out of the alloy
as it is present in such a small quantity. The cost of maintaining
the accuracy of assay is a big reason the micro alloys have not
caught on in the general marketplace. So I can’t believe that a
refiner would add zinc just to aid in manufacturing of such a
ductile metal as gold. I am not a granulation specialist (I have done
some, I took a workshop with Kent Raibie and one with Doug Harling
years ago) but I think Noel’s problems stem more from overheating. If
she is not adding copper to the area of the bond then the bulk metal
will be way too close to melting when the fusion occurs and the
amount of silver that will flow will be too great and cover the
surface of the gold.

Jim