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What happened to my silver?


#1

Hi all,

I’m new to metalworking and this is my first post, so go easy on me.
:wink:

So, I melted down some of my silver scraps to reuse as sheet, and
the melting and rolling seemed to work fine. However, each time I
annealed it, and again when I soldered a bezel to it, it kept
reticulating or something. In some of the gas bubbles it almost
appeared to have rust. but the pickle never contaminated, so it must
not be iron. or at least not an abundant amount of iron. But, it does
seem like it must have been some sort of contaminant, but what? And,
is there a way to salvage it? What I melted down was mostly sterling
silver with a little fine silver mixed in, and probably some silver
solder as well. Next time I will definitely run a magnet through my
scrap just to be sure there is no iron, but if that’s not the
problem, then that won’t help.

Does anyone know what this could be, and what I can do about it? I
attached pics of the surface and cross sections so you can see what
it looks like.

http://www.ganoksin.com/ftp/IMG 0415.jpg
http://www.ganoksin.com/ftp/IMG 0421.jpg
http://www.ganoksin.com/ftp/IMG 0419.jpg

Thanks in advance for your collective wisdom. :slight_smile:

Melanie


#2

Hello Melanie,

You indicated that there was solder in the mix of metals you used.

I couldn’t open the photos, but based on your description, most
likely that is causing the problem. Time to just put it in the
refining container. In the future, if there are solder joints in
scrap, either cut them out or plan to refine. BTW, chains are full of
solder.

Judy in Kansas, where the hummers are hitting the feeders and
putting on some grams to get ready for the long migration.


#3

Judy, something got crossed. Your answer is not my question. I
wanted to know if cuppric nitrate would help me “dye” my turquoise
that has turned green over time. Also I have a piece that got
bleached by a cleaner and it removed the color. AND WILL COPPER
NITRATE HARM THE SILVER OR STAINLESS THAT IS SURROUNDING THE
TURQUOISE? Thanks in advance! Diane


#4

Melanie,

it sounds like something in your scrap was not sterling but silver
toned metal (broken chain scraps most likely).Silver jeweler’s
solder doesn’t generally contain iron unless it’s a plumber’s solder
that says something like “silver bearing”-Most of those solders are a
small percentage of silver (10% silver to maybe 40% if you buy the
best of that type) and tin, zinc, antimony and sometimes bismuth -
buy plumb gold and jeweler’s solders (Hoover & Strong’s is the brand
most vendors carry and is also available from the manufacturer with
an account to buy from them. They supply many melt points of each
type of solder for all purposes at the bench. If you like or need
some paste solder and don’t make your own -yet- My Unique Solutions’
Beth Katz makes a good variety of silver solders and offers a good
range of melt/flow points in each grade as well as a powdered silver
solder that you usually have to order about a week in advance as she
sells it out fairly quickly after producing it.) and you have iron in
the pour.

The pickle pot’s ceramic or “stoneware” liner can cause all sorts of
problems that aren’t apparent until you realise that stoneware is
essentially kaolin clay with impurities like iron and carbon, micas
and quartz that is partially vitrified when fired so it is still
somewhat porous from the metalsmith’s perspective. After we put an
acid solution in it and heat and reheat it and leave it in the
stoneware overnight, night after night, it eventually leaches through
the glaze and voila -iron contamination -.In fact those using a
slow cooker for their pickle pot often begin to see inexplicable
inconsistencies in their work after pickling even though they may
have used the same procedures successfully many times or just mixed a
fresh batch of pickle. From discoloured metal to hazing, film that
seems permanent to the point of having to be removed with abrasives
when the contaminant is the pickle pot its not usually the first
thing one thinks to look at as the root of the problem when often,
it is the cause of everything going wrong, and is worse the lower the
grade of pickle pot to begin with. Buying a professional model with
an acid resistant liner or die pressed copper insert are the best
things to use.

Using a magnet before placing any silver scrap into the crucible
should become habit. You never know where that broken bit of saw
blade wound up when it went flying or dropped onto your sweeps tray!
And then there are the obvious solder joins from inherited scrap that
should always be cut out often not worth the time when silver casting
grain is below 20 bucks an ounce.

Reticulation silver is 80 % silver and 20% copper - what you have
doesn’t sound like a silver copper alloy- there’s some other
contaminant in it.

Using a carbon rod when the molten silver is spinning in the
crucible to pick off any film of impurities that has risen to the
surface of the “ball” is effective. You just have to use more gasses
and it adds time to the melt to have to keep it rolling until nothing
else surfaces and you have a smooth molten ball of metal left in the
crucible- and the rod helps mix metals if you are making your own
sterling or silver alloy or karating gold up or down, or colouring
it.

As for solutions,: roll it out as thin as possible and cut out any
problem areas. Melt again in a well glazed crucible (use pure borax
not 20 mule team as the fillers are sometimes clay based) with a few
pinches of refining flux (add to say 2 Tbsp of crystalline borax from
a cone, a half teaspoon of sal ammoniac / ammonium chloride which can
be readily gotten from a stained glass supplier as a tinning block
for soldering irons. Keep the block in a completely airtight
container after opening as it will readily absorb humidity from
ambient room air. Mix the two ingredients well and keep tightly
closed in a glass jar with a plastic or compound/resin lid, like
those in which spices are sold. A few pinches is all you need to add
to molten metal to help impurities rise to the surface of the
mass).Use a carbon rod to mix well and dip off anything that floats
on the ball of molten metal(have a cast iron pan with sand nearby to
cast the impurities into- or any vessel that is heatproof and has
some annealing grain, sharp sand, or other abrasive and heat
absorbing qualities that will help you remove any crusts that form on
the rod into safely.

if you have any further questions feel free to contact me. rer


#5

I mainly roll my scrap into wire. I have learned to keep my clippings
and other larger pieces separate from filings. I don’t even try to
recycle filings. They get bagged up and go to the refinery. Before
melting I use a magnet to remove any pieces of ferrous material (file
debris, saw teeth, etc), and cut out as much solder as I can. You
need to heat your mold to drive off any moisture and make sure that
there aren’t any little pieces of metal left from the previous cast.
I heat the mold before I assemble it. Once assembled, melt your scrap
completely, add a little Borax, and pour it as quickly as you can
with out missing the mold or over filling. It helps to have some idea
how much by weight each mold will require and try to melt just a bit
more so that you don’t over fill the mold and scatter melted metal
all over your work surface. Break open the mold once you can handle
it (wear gloves), remove the ingot and cool it off in water. Inspect
it closely. Wire molds will have an obvious crack (at least mine do),
where the ingot has shrunk but the button at the top pulls back. You
have to remove the button anyway, so do it at the fracture. This may
be mold specific and not true of all molds. It is, however, the case
for both of my molds. Keep inspecting. Look for seam flashing. It
should be removed. I use a lapidary sanding belt to smooth the ingot
all around and on both ends. Forge the ingot in as many directions as
you can without changing the shape relative to your final desired
shape. Anneal as needed and then begin your rolling. I usually anneal
before my first forging and definitely before you roll. If you find
obvious problem areas, remove them if you can and continue rolling.
If removing them means the piece can’t be used, remove them anyway
and start over. This all sounds very tedious, but it works for me and
saves a lot of frustration, self doubt, and, in the long run, time. A
couple of tool suggestions. Go to a decent hardware store and buy a
small bolt cutter. You will be surprised how many times this is your
go to tool. You can build a temporary safe casting area out of
hardeeboard (tile backer) that can be removed once you are done
casting. I cut the hardeeboard into a variety of smaller pieces and
one large one to work on. I have looked at the Hardeeboard MSDS and
have not found any environmental problems from using it as a
temporary heat shield. If anyone knows otherwise, please reply.
That’s about it. There is a lot of on Ganoksin about
recycling, rolling and casting. Some of it is very quantitative, from
a metallurgical point of view. The above is my distillation of it.
Good luck. Rob

Rob Meixner


#6

Thanks everyone! I can’t remember now how much solder might have
been in there, or if I heated the mold up enough or not. But these
responses have been very educational, and I really appreciate it!
Next time I will be much more rigorous about how I melt down my
scraps.

Melanie