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December 10, 2018, 07:52:46 am
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Reusing scrap silver

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Author Topic: Reusing scrap silver  (Read 1355 times)
GregHiller
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« on: July 17, 2014, 12:45:47 pm »

I have a fair bit of scrap Argentium piling up and was looking to turn it back into some useable flat sheet material.  I've already used some to make decorative balls, but I have enough of those at the moment. 

Any idea of the best way to do this?  I have a steel rolling mill.  I was thinking about cleaning the scrap carefully in some pickle, then melting it all down and pouring it into a mold of some sort.  I don't have the mold at the moment, so was wondering what I should get.  I do have a graphite crucible I think I can melt it in, either with a torch (I have a oxy-acetylene cutting torch that would probably do the job) or in an oven.  What do I need for a mold?  I've seen graphite, cast iron, or steel molds.  Sounds like you need ingot mold lubricant with the steel molds?  Is the graphite mold likely to yield a reasonably flat piece that I can run though my rolling mill, anneal, and repeat until I get to my desired guage (probably 22-24)? 
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« Reply #1 on: July 17, 2014, 12:51:23 pm »

Can't help on the 'what to get' part, but make sure there is no solder on the pieces before you make your ingot.

I have a friend that casts and he says mixed in solder really goofs with his casting.
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« Reply #2 on: July 17, 2014, 01:00:06 pm »

I routinely cast ingots and roll them into sheet. I use the simplest form of mold: tufa stone.  Tufa allows you to carve a simple mold and cast a shape specific to your needs. You can cast an ingot that will roll out into the basic piece of sheet you need for a given piece of jewelry, or you can cast an ingot just the right size to make a sheet that will maximize the working yield from your mill.

My scrap bucket has numerous scrapped jewelry pieces with solder on them. It has never caused me any problem.

I've posted a couple threads on this site that show the process for casting with tufa. I'll see if I can find you some photos for a useful example. Be right back!

OK, I'm back!

Here's part of a tutorial I did last year, showing how to use tufa to cast a specific jewelry part. If you were going to make sheet, simply carve your ingot mold wider, and run it through the mill a few more times.

(snip)

I started the project with a pile of scrap silver, which I cast into an ingot using tufa stone. The ingot will be about 1/4 inch square, and a couple inches long.



Here's a picture of the ingot still in the tufa, and then after removal. Removal is easy with most tufa castings, since the metal tends to shrink slightly as it cools and hardens after casting, allowing it to pop out of the mold easily. If you have never done casting, tufa is the simplest, cheapest way to get started. It's very forgiving and easy to work with . . . cheap too, as casting methods go.





Next I removed the tiny branches from the side. They form in the diagonal passages that point upward from the ingot mold, allowing air to escape as you pour the molten metal into the mold. Metal nearly always runs partway up the passages, leaving those diagonal branches. I used a simple file to remove high spots from the casting before I started rolling down the ingot. The ingot went straight from this photo into the rolling mill.



Here's my favorite toy. You can see a two inch wide flat portion of the rollers on the right side that is used for rolling sheet. That's what I will use for this ingot. It makes the ingot slowly longer and thinner, but not much wider. The slots you see on the left side of the rollers will make square wire in a number of sizes.



 Here's the ingot after the first pass through the mill. I usually roll an ingot through the mill in numerous stages. If you try to squeeze too fast, the rolling is hard, and you are more likely to create cracks along the edges. This is after about three passes through, each pass taking another small bite into the ingot to thin it.



I typically pass an ingot through a few times. After that it begins to work-harden, and I need to anneal it before  a few more passes through the mill. To anneal it I simply heat it cherry red on a piece of asbestos and then lay a second piece of asbestos over the top and let it cool at its own speed. That tends to soften it up a whole lot, allowing me to flatten it again and run it through the mill to thin it a bit more. Here's what the ingot looks like after annealing, straightening, and a bit of polishing:



And here it is after the next three passes through the mill. Thinner, longer, work-hardened again, but ready to use. This is the thickness I had in mind.



And here's the result I was aiming for (along with the left-over piece): a quarter inch wide, eighth inch thick piece of low-dome half round wire, cleaned up, polished, and ready to shape into my finished design. I simply cut it to length and shaped it with a hand file.



(end snip)
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Bentiron
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« Reply #3 on: July 17, 2014, 05:40:21 pm »

You can use a charcoal soldering block as mold also, I've done that.
Now as to using silver scrap with solder, yeah, you can do that but then it is neither fish nor fowl, it isn't Sterling silver any more but a very high grade of silver solder if it has zinc in it. You can't stamp it .925, so just what is it? I have always separated out the scrap as to clean and dirty, that is with and without solder. I saved my dirty silver for years and finally struck it rich when silver hit the near $50/ounce price, a wonderful payday for me.
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guest787
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« Reply #4 on: July 17, 2014, 05:58:23 pm »

Actually if he takes the scrap that has solder in it and adds in fine silver in whatever proportion it takes to get to sterling he'd be fine with the sterling mark.   dunno
I remember reading an article once where they were talking about using scrap with solder, and this was how they got their silver to be sterling was to add fine silver casting grain to the pot.  I however cannot remember the exact formula that was used nor which magazine I saw it in.   The longer I go without working the more I swear my brain is lapsing in memory.   bricks
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Isotelus
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« Reply #5 on: July 17, 2014, 08:20:23 pm »

Clean Argentium Scrap is best for remelting which works well. Just keep the soldered pieces out of the ingot melt.

Solder will show up as spots in your metal as you roll sheet or wire from it. It won't make you very happy either.
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Bryan
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« Reply #6 on: July 17, 2014, 09:56:24 pm »

In Tuffa casting as a mold release the Indian smiths I know. Use candle soot, just hold the carved mold over the flame of a regular candle & let it get well sooted. Kind of fills the grain in tuffa & lets the piece release better without pulling pieces of the tuffa with it.
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Cowboy
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« Reply #7 on: July 17, 2014, 11:44:07 pm »

In Tuffa casting as a mold release the Indian smiths I know. Use candle soot, just hold the carved mold over the flame of a regular candle & let it get well sooted. Kind of fills the grain in tuffa & lets the piece release better without pulling pieces of the tuffa with it.

Yep. Candle soot will work, or even better, if you use an oxy-acetylene torch, the soot from a pure-acetylene flame will quickly coat a tufa mold and help release your casting.

I've found that castings release easily from tufa, even without any soot, when you carve the mold with slightly tapered sides.  Then, let the silver cool a bit before you open the mold. The silver shrinks a little as it cools, and naturally pulls itself free of the tufa mold.
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GregHiller
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« Reply #8 on: July 18, 2014, 07:17:22 am »

Thanks all.  I think I'll purchase some tufa stone for casting.  I see it's available at Thunderbird supply.  This should be fun.

Most of the Argentium that I have does not have any solder in it, but if I do include a few small pieces with solder (basically screwup designs) I would think that when you melt things well the zinc would mostly get mixed in well.  The amount of solder that I'd consider including would be so minimal that it would be far less than 0.1%. 

> the soot from a pure-acetylene flame will quickly coat a tufa mold and help release your casting.<

Works great to coat the walls of your garage as well!!  Been there, done that!
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Bentiron
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« Reply #9 on: July 19, 2014, 05:30:31 pm »

Cuttle bone also works as a mould for casting ingots.
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« Reply #10 on: July 20, 2014, 11:12:46 am »

Also remember to run a strong magnet over the scrap to remove any steel.  If  you do use the oxy-acetylene cutting torch  use it with a reducing flame. have some borax on hand to clean the metal before the pour.
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David

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« Reply #11 on: July 20, 2014, 11:23:28 am »

I have been melting scrap and making new sheet and wire for at least thirty years perhaps longer. This said here are a few points I would like to make.

Solder with scrap...... If it is just a bit of solder no worries as long as you get the scrap melted to the right temperature and then stir it with a carbon rod very well prior to your pour.

Rather than all of the trouble of using tufa cuttle or charcoal. There are many steel ingot molds available if you do a search at Rio Grande for ingot mold you can view 10 different styles. I have both the open what is called a wire mold and also the adjustable type similar to the image I am posting. Heat the mold up a bit prior to the pour, it only has to be 300 plus degrees.

Prior to starting with the rolling mill it is best to hammer the ingot with the edge of a ball peen hammer (I have one that has a flat ground on one edge that is the rounded), in doing this you kind of even everything out so there are no soft spots that can cause problems with your sheet or wire.

You need to anneal your piece when it gets hard for you to roll it, when annealing heat the piece up to a dull red and let it cool in the air “do not quench it as this just hardens the metal”.

So you all know what I am talking about I have also attached a few images of hammered bracelets that I was making in the late eighties and early nineties. All of the shanks were made from scrap that was poured into an ingot mold and then hammered on an anvil to give me my shank. This type of shank typically is thicker in the middle and thinner on the ends. On the three tear drop row bracelets in the one photo and the photo of the side in the other, the bead has been raised not soldered on, this is far from easy but the results are wonderful.

Hope this is of some help.

All my best ............ Danny


* bra9.jpg (50.58 KB, 500x400 - viewed 9 times.)

* bra6.jpg (53.2 KB, 716x400 - viewed 6 times.)

* row4.jpg (62.09 KB, 920x600 - viewed 7 times.)

* row3.jpg (55.11 KB, 546x600 - viewed 9 times.)

* 704108.jpg.png (111.44 KB, 699x700 - viewed 7 times.)
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Cowboy
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« Reply #12 on: July 21, 2014, 12:41:56 am »



Rather than all of the trouble of using tufa cuttle or charcoal. There are many steel ingot molds available if you do a search at Rio Grande for ingot mold you can view 10 different styles. I have both the open what is called a wire mold and also the adjustable type similar to the image I am posting. Heat the mold up a bit prior to the pour, it only has to be 300 plus degrees.

I never thought of tufa as much trouble, but I'm gonna try your advice anyway . . . mostly because a retired silversmith advertised his used tools on craigslist today. I bought the whole collection, and among the goodies were two steel ingot molds.  One is almost identical to the one you posted.
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« Reply #13 on: July 21, 2014, 01:45:26 pm »

I have a reversible ingot mould, flip it one way to make ingots for sheet and square bar, flip it the other way for a variety of round ingots, a very handy mould. I also have two older cast iron moulds that I got from who knows where that were used for making wider sheet than my rolling mill can accept so I used them to make bronze sheet ingots to forge out for pieces of my sculptures. A friend told me big commercial jewelers used this type of ingot mould for in shop recycling of clean silver & gold scrap. I, too, smoke them up acetylene soot & warm them prior to casting ingots.
I think the suggestion of tufa, cuttle bone, charcoal block & and other material for ingot moulds were suggested as alternatives to spending a lot of money on an ingot mould just to experiment with the process of making and ingot. When I was doing a lot of bronze casting, doing something with left over metal was always a problem, one solution was to make ingot moulds of various sizes out of bare steel angle with the ends cut at 45 degrees, this made very nice ingots, every thing from 1/2" up to 4" angle was used. I also used an old rusty cast iron cornbread pan in the shape of ears of corn, those looked  nice in bronze(LOL)
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Cowboy
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« Reply #14 on: July 21, 2014, 01:54:24 pm »


I think the suggestion of tufa, cuttle bone, charcoal block & and other material for ingot moulds were suggested as alternatives to spending a lot of money on an ingot mould just to experiment with the process of making and ingot.

Yep. That's precisely why I suggested tufa: lots of people on this site seem to be looking for ways to enhance their hobby without spending a lot. I've been happily using tufa for many years, though I'm excited to try a proper steel ingot mold now that I've got my hands on one.
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« Reply #15 on: July 21, 2014, 02:40:16 pm »

>You need to anneal your piece when it gets hard for you to roll it, when annealing heat the piece up to a dull red and let it cool in the air “do not quench it as this just hardens the metal”.<

I don't work with sterling much, and that might be the case for sterling, but for Argentium I usually let it cool Very slightly just so it's no longer brittle, then I quench very quickly.  This gives me a very soft piece.  I found this section on the PDF for Argentium FACS:

>On the other hand, note that the sooner the Argentium is quenched
after it reaches black heat, the softer it is; therefore, you may
choose between metal softness and the risk of shock-cracks
or warpage according to the situation and your personal
sense of concern about those factors.<
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« Reply #16 on: July 22, 2014, 05:22:31 am »

Broomstick casting is a technique that you can use for all your scrap that has solder in it. If you do a search for "broomstick casting"( as my computer skills are very lacking in posting links. dunno ) you will find many good articles on the topic.  It is extremely easy to do.
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GregHiller
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« Reply #17 on: August 05, 2014, 07:23:43 am »

So, I tried the Tufa stone casting method to try and make sheet silver out of my scrap.  It was quite easy to shape the tufa stone, and the material was very inexpensive from Thunderbirdsupply.  It only took a few seconds to cover the tufa with some soot from my acetylene torch (no O2 going in).  I was working with Argentium.  The problem I had on this initial try was warned about by an earlier poster.  I also realized the problem after reading a little more carefully some of the Argentium literature.  Indeed, for a small thin piece of Argentium you can achieve maximal softness by quenching quickly after annealing.  However, for a thick piece which cools much more slowly you must be more careful.  I clearly created thermal shock in my piece the first time around which showed itself as I began to roll the material out.  When I tried again (I just remelted my failed attempt) and allowed the thick piece to cool more slowly before quenching I did not have any problems.  However, I will say that this is a SLOW process.  I needed to anneal the piece many times between rollings. 

I suggest to anyone doing this, if you are trying to get back to sheet material, you are best off making a mold that yields an ingot no more than 2-3 mm in thickness.  Also, if you have a roller that can deal with large pieces you are much better off.  The flat section of my roller is only 1" wide.  As I rolled the pieces sometimes they would twist a bit so it took some patience to keep them rolling in the center (the flat) section of the roller.  As I worked the ingot down I eventually cut it into multiple pieces as it got longer and longer and more difficult to handle.

All in all it was a fun process.  I learned a bit and the final result was good.  The material I ended up with looks every bit as good as a new sheet from Rio, albeit a bit narrow!

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« Reply #18 on: August 06, 2014, 12:38:13 am »

Fantastic!  Learning is always a good thing.

You're making me appreciate my mill a bit more. I often wish the flat roller was wider, but mine is two inches, which must seem generous to you!
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