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deleted
35 Posts |
 Posted - 06/20/2007 : 04:45:25
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hi again,i hope i'm not being a pest but it's better to have more knowledge than less!
what are the melting points of gold and silver?
if i wanted to make an ingot/bar from say 20 .999 coins would the restulting molten metal automatically be .999 or would it be tarnished by what ever i was melting it in?
many thanks
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Ardent Listener
Administrator
USA
4841 Posts |
Posted - 06/20/2007 : 06:50:02
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Here is a link to a list of melting points for a lot of metals.
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Fanaticism is doubling one's efforts, yet forgetting one's purpose.
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pencilvanian
1000+ Penny Miser Member
USA
2209 Posts |
Posted - 06/20/2007 : 08:07:47
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Silver melting point 961.78 C
Gold melting point 1064.18 C
I have no experience in melting metals myself. I doubt that the .999 silver would be altered or contaminated by pouring it into a clay or metal mold.
I tried researching the net for "silver ingots" in hopes of finding some advice on making them at home, but most of the links lead to the "final fantasty" game.
Here are a few information links to get you started
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I do not know if you will take this route or use a torch that the jewelers use, but here is a good place to start your research:
Quote:
Stan, I melt silver in the 1-3 oz range using my coal forge and a stainless steel creamer...
...---I like using the 1oz rounds in fine or sterling or coin silver---laying flat in the bottom of the creamer, a little borax or powdered charcoal is suggested to keep O2 out of the metal...
...Heat, not so fast that a lot of O2 makes it through the fire, not so slow that there is a lot of time for the metal to take up O2. Pour when the surface is swirling.
I take the top of the creamer's off to make it easier to pour but put them loosly on top to reflect heat back in and keep flyash out. Remove before pouring....
...SAFETY!!! Molten metal is a lot more dangerous than hot steel even if the steel is at a higher temperature! Any trace of water in the mold can result in an explosion of molten metal back onto yourself. Aprons, gloves, face shields ---all mandatory!
If you have not worked with molten metal before work through a pour with someone who has!
*****
I don't want to scare you off, since there are electric furnaces that jewelers use to melt their scrap gold and silver down to reuse, but safety is a must when melting anything, be it metal, wax, anything.
....Did a bit more digging.
results so far.
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Excerpt:
...Also, it's important to be aware, when melting fine silver, that it has an enormous ability to dissolve oxygen from the atmosphere. This doesn't hurt it, per se, but it then comes back out of solution as the metal solidifies after being melted, which can often cause major problems with porosity in the solidifed metal, unless considerable cautions are taken, while melting, to exclude atmospheric oxygen from the silver melt. It's harder to do than melting sterling silver, since with sterling, the copper scavenges some of that excess oxygen, and then, at least with molten sterling, slags off, helping to keep the melt relatively cleaner. Also, sterling silver melts at a substantially lower temperature, making it easier to melt, and it melts over a temperature range, rather than all at once at a single temperature as does pure silver. This makes it much easier to obtain solid structurally sound cast metal, than with fine silver, which tends to porosity and shrinkage cavities in the castings. If your bars are fine silver, and you wish sterling silver, then add copper as you melt the metal. The total composition of the total weight of the melt should be 92.5 percent silver and 7.5 percent copper. Electrical copper wire is an easily found source of high purity copper if you want. To melt the two together, melt the copper first with about an equal amount of silver, stirring/mixing the melting metals together until the copper is completely dissolved. Them melt this with the rest of the silver.
In both cases, be sure to use a proper melting flux, usually boric acid, or a mix of boric acid and borax, to protect the surface of the melting metal.
The above assumes that you're intending to produce cast jewelry, or otherwise cast forms. It's also valid if you've got the tools to draw wire or roll sheet metal, but from experience, I'd note that getting good quality sterling silver sheet metal from ingots you pour yourself is harder than it would seem. Sterling is prone to oxidation enough that getting a really good clean ingot is quite tricky. Your end sheet metal is quite likely to have some good areas, and some flawed areas. Don't expect to get resulting sheet metal that's the equal of commercially produced silver sheet metal.
Wire works better, especially when you use the closed type of ingot molds that produce a long narrow bar from being poured into one end, rather than the open groove type of wire mold (these molds work fine with golds, especially higher carats, but not so well with silver).
Witn wire, even when the ingot has flaws, the resulting flaws tend to become centered in the wire as you draw it, so though the wire may not be perfect, it's often still quite usable. Flaws in silver sheet usually form blisters/bubbles the first time you heat the metal to anneal or solder it. And of course, if you have fine silver bars, and want fine silver sheet metal, just roll the bars out as is, without another melting operation. So then. Still ready to just melt and use your existing silver bars? One other factor to consider... Silver is cheap. The bars are sold at full market price for the silver, and often a bit over for the nicer bars. They're easy to sell in that form. Silver sheet metal and wire stock is more costly, but not really so when you consider all the work and cost that goes into changing the raw metal into usable sheet metal and wire. The commercial refiners are experts at this, doing it very well and efficiently. If you compare costs to buy ready made sheet metal and wire vs the cost in time to make it yourself, you may find that their prices are very reasonable.
End Quote.
Good luck on your ingot making.
I should have chosen "Cut-n-Paste" as a forum name, since that is what I do, mostly. |
Edited by - pencilvanian on 06/20/2007 18:44:31 |
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pencilvanian
1000+ Penny Miser Member
USA
2209 Posts |
Posted - 06/20/2007 : 19:02:52
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Did a bit more digging,
sometimes you have to ask the wrong question to get the right answer, I searched for "casting gold and silver ingots"
and found this website.
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If nothing else, at least you have a resource to go to in order to get help in your ingot making.
Their ask a question page,
You must be logged in to see this link.
Again, good luck. Post any success you encounter.
I should have chosen "Cut-n-Paste" as a forum name, since that is what I do, mostly. |
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smelting point
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