smoothing a silver bar O.o

[Woolf]

i have been melting down my 925 silver to make room... just curious what is the best way to smooth a bar? some edges are sharp and some are just rocky ( very small bumps ) should i use a metal file? or would that ruin it.... lol

 

[nickvc]

Sounds to me like you haven't let your scrap reach full melting point.
When I'm melting I like to make sure the metals are all fully molten,experience helps but if your not sure use a graphite stirring rod and stir your melt which I do every time anyway, if it's not fully molten you will feel the lumps of metal as you stir, use a flux to remove the oxides and make sure you warm and coat your mould,I use wd40,before pouring your metal into it.
Never introduce cold metals into molten metals!
Wear proper protection at all times when melting!
Be aware that melting metals can be extremely dangerous!
These warnings come from personal experience

 

[philddreamer]

If I may add a note, silver also has an affinity to oxigen; the purer the silver, the greater the attraction. Yeap... I also had one of those moment, too! There're some post on GALLERY - "My first silver buttons".
Some of the members expirienced with melting silver the right way, came to my rescue. 8)

I hope the info is of help.

Phil

 

[Harold_V]

A well seasoned (blackened) preheated mold will eliminate the vast majority of your complaints, but if you find an ingot with sharp edges, do remember that silver is VERY ductile. You can tap the sharp edges and blend them nicely with the body of the ingot. I don't recommend you file---no need to make scrap from your ingot. I do recommend you heat a little hotter, and learn to season the mold properly. Blacken it with a sooty acetylene torch, then heat it to just below the point where the carbon starts to sublime. That should yield a more smooth bar. Also, play a reducing torch on the surface as it cools, to control cooling and shrinkage--with the added benefit of consuming any liberated oxygen, and preventing the molten silver from absorbing any more.

You shouldn't have much trouble with oxygen with sterling scrap. You can expect the surface of the bar to be discolored if you use excessive oxygen, however. Try to melt with a neutral flame.

Harold

 

[Woolf]

hmm i was just putting my ingot on the stove and heading it up lol wasnt adding anything to the metal.. or ingot.. my furnace runs at 1850 should i put it higher? i also use a electric furnace sometimes it shocks me so i dont really enjoy stirring the metals haha

 

[butcher]

For my sterling (thin scrap) that I will use later for inquarting gold, to make room for storage, I cut it in small pieces with tin snips and diagonal cutters, and store it in jars, this gives me small pieces, with differing weights which make it easier to fit melting dish and weighing amount needed for inquating later.

 

[Harold_V]

hmm i was just putting my ingot on the stove and heading it up lol

Likely not hot enough, although it will work, yielding the results you mentioned. If your mold is hot enough, the metal you pour won't freeze instantly, which is what causes those sharp edges. Key is keeping them molten long enough to settle in with the balance of the metal.

wasnt adding anything to the metal.. or ingot..

I didn't imply you should. All I talked about was seasoning your mold well (carbon, or soot), and preheating properly. Without that, you can expect continuing problems.

my furnace runs at 1850 should i put it higher?

Likely not for sterling. Just preheat and season the mold properly.

i also use a electric furnace sometimes it shocks me so i dont really enjoy stirring the metals haha

Understood! I wouldn't, either.
Are you using one of those small electric melters that use a graphite crucible? If so, keep the cover on while you melt, which will increase the crucible life, plus it minimizes any exposure to the atmosphere. If that's what you're using, your individual pours shouldn't lose any heat until they have been poured, so the temp you suggested is likely high enough. If, however, you are melting in an oven, removing the vessel with tools, and handling a few seconds before pouring, it is possible you are pouring too cold. Experiment a little and see how it goes. None of these guidelines are carved in stone, if for no other reason, your circumstances may be very different from those of another. What works for him may not work for you as a result.

Harold

 

[Woolf]

yes im using the HandyMelt furnace lol can hold up to 3 kilos i only use a 30 oz crucible though... i preheat then place crucible in at 1850 temp dropd down then reheats back to 1850 then i put my scrap sterling inside then i heat my ingot on the stove ( im worried the oven will melt the clamp that holds the ingot shut ) and then i pour inside the ingot

i do keep the top on while heating lol im told a crucible only lasts 10-15 use's this true? dont want it cracking open while i try transfering to ingot

 

[Harold_V]

yes im using the HandyMelt furnace lol can hold up to 3 kilos i only use a 30 oz crucible though...

If you read enough of the old posts on this forum, you'll encounter the thread(s) where this furnace has been discussed. I owned one and let it sit idle on the shelf for years. I hated the damned thing. Note the GSP shares my opinion. Crucibles are expensive and last only briefly, which will be the answer to your question, below. I even tried coating the rim with a refractory wash to prolong it's useful life, but with less than acceptable results. Once you go beyond the combustion temperature of carbon, they go away quickly, and that's well under the 1850° you mentioned.

im worried the oven will melt the clamp that holds the ingot shut ) and then i pour inside the ingot

Of what material is the clamp made? Even if it's aluminum, it should withstand the temperatures involved. You don't want to get the mold to the point where carbon sublimes---it defeats the purpose. I would suggest that the mold be heated to something like 800°, although I never did establish what was an acceptable temperature. I simply stayed below the point of losing carbon blackening.

i do keep the top on while heating lol im told a crucible only lasts 10-15 use's this true? dont want it cracking open while i try transfering to ingot

The experiences I had didn't yield that result, but I also used the furnace to pour---I did not remove the crucible. I'm surprised that you are, if you are. On the model I had, that was not required.

The head of the crucible goes away first, rendering it useless because you can no longer pour as desired. The burning head acts to eliminate oxygen, so there's not much activity below the rim. Unless you flux, the remaining body of the crucible is likely to be in reasonable condition when the head is long gone.

You can torch melt your silver easy enough, using a large melting dish. All depends on how large the ingots are. If they're too big to pour from torch melting, you might consider building a small gas fired furnace. Easy to build, and much nicer to use. They can be fueled by natural gas or propane.

Harold

 

[Woolf]

i thought about torchs but went with a furnace figured it would cost less in the long run ( with rebuying gas ) but guess i was wrong considering a crucible cost 15$ lol... i can pick my furnace up to pour dont know why i havnt tried that..