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 Post subject: Melting Furnace Reviews?
PostPosted: Thu Jun 09, 2016 5:06 pm 
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I 'm thinking of buying a new (or good used) digital melting furnace for small-scale jewelry casting (gold and silver only). The one I'm strongly considering is the Handy Melt 110 v., 30 T. oz. capacity, made in Italy. In checking around I see there's a flood of Chinese-made furnaces at a much lower price. While the price is attractive I'm a little leery.

Does anyone here have experience/recommendations on this topic? The comparable Kerr model is a little too spendy for what I have in mind. Thanks in advance for any suggestions.

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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Thu Jun 09, 2016 11:01 pm 
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Can't give advice, not enough experience but jewellery making is the logical next step for me and I'm intrigued at this piece of equipment. The club I used to belong to used an old-fashioned ceramic crucible, heated with a oxy-acetylene torch. It spun around at high speed when released, forcing the molten metal into the cast. This looks like a rather more advanced device.

Looks like it runs on the same principle as the aluminium smelter in my hometown. But I didn't think it would work on such a small scale.


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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Thu Jun 09, 2016 11:07 pm 
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The first time I watched them do it was a bit unnerving - they yelled out "fire in the hole!", released a trigger and the crucible full of molten metal spun around at high speed in the centrifuge, while I dived behind a bench and cowered there :) I guess you'd get used to it.


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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Fri Jun 10, 2016 4:21 pm 
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Lefty, there are several problems with torch-melting for casting. The main ones are proper temperature control and oxidation of the casting metal, both of which can result in bad casts. A melting furnace ideally will prevent both of those but at a price...

I torch-melted for years but because of those problems I've been sending my waxes out for casting in recent years. But that's a bit of a hassle especially the time involved.

I've seen a couple of gold-decorated walls in my time (not mine fortunately) due to blown flasks and improper shielding around the centrifuge. With careful investment procedures and properly-installed shielding, often as simple as an old galvanized wash-tub, centrifugal casting is very safe. Vacuum casting is even safer. But attention to proper procedures is always primary any time open flames and melted metal are involved.

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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Sat Jun 11, 2016 1:13 am 
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So what do you do with this particular device Rick? Just pick it up like a pot of hot coffee and pour into a mold? I thought the idea of th centrifuge was to drive the molten metal right down into the cast before it had time to begin hardening. Do you still need a centrifuge with this set up?


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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Sat Jun 11, 2016 1:35 am 
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Lefty wrote:
So what do you do with this particular device Rick? Just pick it up like a pot of hot coffee and pour into a mold? I thought the idea of th centrifuge was to drive the molten metal right down into the cast before it had time to begin hardening. Do you still need a centrifuge with this set up?

It's only for melting metal Lefty. The metal goes into a crucible inside the furnace and the lid is closed to prevent air (oxygen) from getting in, The digital models allow pre-sets to bring the melt to whatever specific temperature is desired for casting.

You still need the centrifuge or vacuum-assist casting set-up. When the metal's properly melted you use tongs to remove the furnace crucible and pour the melt into the pre-heated centrifuge crucible and hit the switch. 'Round and 'round she spins using centrifugal force to shoot the metal into the mold. Vacuum casters use atmospheric pressure instead of centrifugal force to accomplish the same thing. Other systems have used steam and air pressure to shoot metal into molds.

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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Sat Jun 11, 2016 2:13 am 
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The handy melt brand has been around for a long time. I am pretty sure they all work about the same. If it were me, I would base my decision on consideration of price, warranty/replacement parts.

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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Sat Jun 11, 2016 5:26 pm 
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The club had a vacuum chamber device but from memory, they used it to suck the air bubbles out of the liquid plaster once the wax cast had been placed in.

So if I was to start doing casting/silversmithing, I'd require a melting furnace, a vaccum chamber like the above, an autoclave-type device to burn the wax or whatever casting material out of the plaster cast and a centrifuge?


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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Sat Jun 11, 2016 9:00 pm 
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Lefty, it depends on what level you wish to begin metal casting. The equipment you mention would set you back some big money. If you just want to learn the principles and do small projects, you need almost no equipment. You can acquire that as you learn. I cast this gold ring (nothing at all fancy but well-cast just the same) using a purchased wax pattern and the following mostly household items for steam-casting:

A short piece of broom handle, a big jar lid, wet newspaper, a terra-cotta flower pot, aluminum foil, modeling clay, an old electric hotplate, a sturdy tin can, some specially-shaped wax sprues, a commercial wax pattern, casting investment powder and of course the metal and a torch to melt it.
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Here's a great steam-casting tutorial by Don Norris:

http://www.myheap.com/chapter-10-steam- ... ?showall=1

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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Sun Jun 12, 2016 3:53 pm 
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Thanks for that Rick. Yes, that equipment would probably cost me more than all my faceting, cabbing and sawing equipment put together. I'll have a go at the steam casting. I do have a quantity of silver I bought when I was a club member. I was going to learn silversmithing but with cabbing and faceting taking up so much time, I never got around to it.

Would silver cast by this method be prone to tarnishing more quickly? ie, more impurities introduced during the process? Not that there's much of an issue I guess, it's not difficult to clean.

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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Mon Jun 13, 2016 12:24 am 
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It sounds like you already have some silver. but if you are looking for silver that will not tarnish, look into ARGENTIUM silver. It is available for casting and should help if there is a tarnish concern.


I am pretty sure that the tarnish from silver is silver oxide, and not impurities from the casting process.


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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Mon Jun 13, 2016 1:39 am 
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wilsonintexas wrote:
It sounds like you already have some silver. but if you are looking for silver that will not tarnish, look into ARGENTIUM silver. It is available for casting and should help if there is a tarnish concern.


I am pretty sure that the tarnish from silver is silver oxide, and not impurities from the casting process.


Yep, the silver merchants I bought the stuff I have carried Argentium silver but I only bought the regular sterling or whatever else it was. Then after I made one small piece I never went back to it and focussed on faceting instead. The stuff I already have might be good for a few practice runs.


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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Tue Jun 14, 2016 10:11 am 
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The tarnish on silver is silver sulphide, sulphur dioxide from the atmosphere fairly rapidly combines with the surface metal. Sweat (especially if you eat a lot of eggs) and certain cosmetics can be a problem also.
At the same time, the tarnish can be a sales opportunity. Have the customer return every few months for a free repolish, but have plenty of new creations to show while they are waiting.


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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Tue Jun 14, 2016 10:14 am 
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On the other hand, if you fancy casting but don't want to spend a lot of cash, look at the Delft process, I have had a great deal of success with it.


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 Post subject: Re: Melting Furnace Reviews?
PostPosted: Tue Jun 14, 2016 12:23 pm 
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This thread has gone very far afield from the original request for melting furnace recommendations. It's partly my fault. Maybe someone should start a new thread about jewelry metal casting.

I've about reached a buying decision but I'm still interested in any comments from *actual users* who might provide insights not obvious to someone who's judging only from supplier advertising. Thanks in advance.

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