MOLD MAKING

Thanks for the reply, it was so informative and with the added warnings! Bit of a Shock That. Over 2 kilos of old and smashed up scrap silver from the past 60 years. It seemed a good idea to make some 1 oz. silver ingots for chains, Oh well back to the drawing board. The reply was super Thanks.

You're welcome.

If you're planning to sell it as jewelry, the physical cautions are the same re: electronic waste in particular. But if there's no electronic waste and you're certain that the stuff is silver (coin or better - that's over 90%) you could do ingot jewelry with your own marks and make a profit.

The cost cautions are not so extreme, because as soon as you put it on a chain it has added value. It's sold as a decorative item, rather than an investment. Sterling silver chain heavy enough for ingots will probably cost you > $5 apiece wholesale, but I would expect that any "ingot pendant on a chain" would easily sell for $40 or $50 on the market even if it is not marked for purity. (Some jurisdictions may require a purity mark on jewelry (?check it out?), but as long as you don't make false claims, I doubt there would be enforcement at the scale we're talking about).

If you stamped a home made ingot "100% recycled scrap silver" "2009" "Made in USA - or wherever you are from" and a serial number indicating the limited edition, they would take on the sort of historical and sentimental value that inspires people to collect. The information is more valuable than the metal itself, because it tells the tale of our times.

If you have over 2 kilos, though, you can get it melted and assayed for maybe around $130 - check around to refineries in your area - some have specials from time to time. 60 ozt or so at $16 per ozt is close to $1000 worth of metal: not bad for the refinery cost alone.

Best of luck.

Thanks Friend, that has explained it all now, and some way to what I wanted to do, keeping it legal etc. I wanted to use a 1 oz. ingot as the mold, without the markings, just for size etc. but getting some thing flexible and for a high heat mixture.

Barry

Go to a Jewelry supply place, and get some Investment. Its a plaster like material that is used for casting. A word of warning -- Make sure (By heating) the investment is dry before poring the metal..If it isn't, the silver will explode (or appear to) because ANY Moisture instantly turns into steam. When doing lost wax casting, the molds are at least 800 deg. Fahrenheit.

Ware a full face shield and non-synthetic clothes (natural fiber) because the synthetics can melt a stick to you, which is not a good thing.

Lost wax casting is not a simple process: the setup to mix the investment properly (without bubbles) and centrifugal casting machine is quite expensive. The object has to be designed with a sprue which allows it to be removed from the mold. Some problems with sprued bars are described - see re-casting hazard if water gets in the casting when quenched. Rubber molds are commonly made, to make duplicates of the wax models used in casting. Wax burnout requires a kiln, produces noxious fumes.. Etc. Expensive setup and multi-stage process (labor intensive). Read about various methods of jewelry casting.

Gravity poured casting is the simple way to go. Graphite is a nice material for a mold - check out the ingot mold design used in this video. Your markings could be tooled on one piece of a two sided mold , hold together with binding wire.

Other mold materials are less durable. Pressed charcoal block can be carved to make simple castings. Not sure if you will have to break it to remove: not too durable I'd guess. Cuttlefish bone is commonly used but they are one off.

It looks so easy (as in the video above) using fine (pure) silver. Not bothering with flux nor worrying about firescale nor needing a pickle to deal with it... Believe me, you save yourself a lot of ??? potential problems by starting with clean, pure metal.

I'd google around if I were you, read all you can find, and be prepared to deal with these and other problems you may encounter with melted scrap.

Ingot molds are made of material the metal does not wet and are smooth sided with enough taper so that the shrinkage on cooling frees the bar. Any legend you wish is tooled into or reliefed up from the mold bottom = top of finished ingot.

To turn into money, Johnson Mathey will give you a quote, but they have a minimum cost. Local buyers will buy for weight and estimated carat grade at a price that favors them.

I reclaim circuit boards, but I ship 2000 poinds at a time.

If your silver has impurities and begins to blush brown-ish as jewelry, you'll also have to worry about the lynch mobs.

I Thought, and was taught, that all silver exposed to light goes 'Brownish' as it is the effect of light upon it, and is a chemical reaction. As in the silver in photographic plates etc. Oh well back to the drawing board and live and learn.

Most of the oxidation that you see in sterling silver is attributed to its copper content. Fine .999 silver will also tarnish - brownish - or develop a mellow color (called 'patina') but it is very tarnish resistant cw sterling and never tarnishes black.

It isn't light that does it: you need water or other trace chemistry to get the reaction with oxygen. Sulfur compounds are used to deliberately tarnish for contrast effects.

Aside from the usual oxides, firescale can be a problem if the silver is exposed to an oxidizing atmosphere - it's recommended to use the reducing part of the flame: the blue or invisible tip of the torch flame - rather than the white part of the flame where there's lots of oxygen.

In a melt situation, boric acid or borax is typically used to deal with oxides and to prevent firescale when soldering. You will save yourself some hassles by making the scrap as clean as possible before the melt. Excess flux can lead to problems too, so read about the experience of others out there on the net. A warm acid "pickle" is used to clean away flux residue as well as firescale.

Silver tarnishes black... A few years ago a lot of impure silver came from Mexico that would form brown deposits on the metal. This was initially the start of the Yugoslavian sitting of Mary and the miracle that silver was being turned to gold. People with good silver didn't experience this effect, and hence felt unfavored by God!