1/4 oz Graphite Ingot Mold

[Noxx]

Hello gold fanatics,
I recently received my graphite mold. I haven't tried it yet but I will soon !
It's smaller that what I taught but when I think about it, 7.77 grams isn't very big. As soon as I will get a nice ingot, I'll post pics in the gallery section.

[IMG::]http://i10.tinypic.com/4pyuh05.jpg[/img]

[IMG::]http://i19.tinypic.com/5x6096d.jpg[/img]

 

[goldsilverpro]

Make sure you preheat the mold with the torch, to drive the moisture off, before pouring the molten gold into it. Otherwise, you'll get spitting.

I like the shape of the cavity of the mold you bought. I have seen some that are sold that are wider and longer, but much shallower. In the shallow molds, it is sometimes hard to get the gold to completely cover the bottom of the cavity. In that case, you end up with an irregular bar.

 

[Noxx]

Of course I'll preheat it

The cavity in the first picture seems very deep but it's not the case. Only a shadow. In the second picture, there are no shadows.

 

[goldsilverpro]

It still looks relatively deep to me. I think you got a good one.

When preheating graphite molds, you can actually see the moisture being driven off, by the color differences on the mold.

BTW, Noxx, when I post, I always consider all 400 members. I know that you are wise enough to preheat the mold.

 

[PhillipJ]

Thanks for the advice on heating the mold GSP. Any of the little things mentioned helps.

And Noxx. What is that larger nugget in the picture from?

 

[Noxx]

It's a gold nugget coming from scrap jewelry. The nugget was in AR and I decided to abort the process before it was completely dissolved. That's why it has this unusual shape.

 

[Noxx]

I haven't been able to melt my 7 grams of gold (directly) in this mold with my MAPP torch. I think the mold absorbs too much heat. Is there something I can do to prevent this ?

Thanks

 

[Harold_V]

Melting in the mold is a huge mistake. Graphite, heated above about 1,100° F burns. It may not burn with a flame, but you are slowly destroying your mold as it converts to CO2 as you play the torch on the mold attempting to melt your gold.

If you are not using oxygen trying to melt, you should. You need a flame that is convincingly hot, not borderline hot enough.

Preheat your mold, then melt your gold in a small melting dish that has been properly prepared. There should be no excess flux, otherwise it will follow the gold into the mold, screwing up your mold and ingot. If you haven't read my comments on preparing a dish for use, ask and I'll repeat the process for you.

The molten gold is heated slightly beyond the melting point, and is then poured into the mold. If the dish is not prepared with flux, the gold will not pour properly, and will likely leave a streak of gold behind. It's important that the dish be adequately coated, and that it be hot enough to permit the molten gold to remain molten until it is poured into the mold.

Don't allow the gold to freeze when it's poured. Play your torch on the surface and allow it to cool slowly. That will prevent the deep pipe, and leave a much smoother surface than you'd otherwise get.

Pouring ingots is a bit of an art----don't be surprised if you don't have great success----and be advised that it's hard to pour small ingots. Temperature control is the issue.

Harold

 

[grainsofgold]

Always used cast iron molds-

Do you need to soot graphite molds like cast iron one?

Also- where is a good source for graphite mold material- I would assume that it need to be of the high density type of graphite- Correct?

I have a good friend with a lathe & mill that can easily cut a cavity into a block of graphite-

 

[Lou]

No, graphite is self-lubricating and quite soft. It can be milled quite easily (with the proper setup) and easily cut with a band saw.


You want the finest grade of graphite available, which is high density and usually called "iso".

I'm making some multiple piece graphite molds, I will post pictures when I'm finished with the machining.


I would really love to get a mold made of glassy or vitreous carbon. Let me tell you that glassy carbon is a wonderful thing! Nothing sticks to it, even Pt does not react with it (graphite would react). It doesn't really oxidise away when compared to graphite.


Lou

 

[Noxx]

Is there any way to get a 1/2 oz or a 1 oz cast iron mold ? It seems that I still have trouble with the too fast cooling of my gold after pouring.

 

[Anonymous]

Why would you melt a gold nugget?

I thought that gold nuggets had more value than the gold content because the vast majority of gold found is fine gold?

 

[butcher]

placer gold is usually not pure gold,the nugget can have value to some people as found, or alot of prospectors in my area melt them to form nugget jewlery and get alot more than gold value, the nugget he is talking about is not a natural nugget,refined gold has a higher value than placer gold (as found) in gold value (if buying for gold value )and not for jewelry (nuggrt)ect. jewelery can have a value 300% of gold value.

 

[Noxx]

No, it's not a gold nugget. It looks like one but it is gold that has been soaked in AR for a while without dissolving the gold entirely.

 

[DNIndustry]

I am going to weigh in on this one.
I bought a graphite crucible and 5oz ingot mold from the graphite store..
The weight designated is the weight of the actual graphite. Not the ingot.

They failed to tell me the crucible needed to be coated in something, else it crumbles. My button had chunks of graphite in it.

Any recommendations to a permanent inner coating for high temp?
Besides a boatload of borax.

 

[Noxx]

I don't think graphite needs to be coated at all...

 

[Harold_V]

Any recommendations to a permanent inner coating for high temp? Besides a boatload of borax.

No one in their right minds would use borax in a graphite mold. You can forget the idea of a "permanent inner coating". That doesn't exist.

If you're casting gold ingots for market, the use of flux isn't a good idea at all unless you have something to hide (dirty gold). It clearly is NOT NECESSARY. Flux is used to mask impure gold, absorbing the oxides from the surface.

If you are casting doré to be shipped for further refining, flux can be useful.

If you find you must coat the mold, do it with a smoky torch. An oxy/acet torch without any oxygen is perfect. Do it either outside, or in a fume hood. The soot generated goes everywhere.

I cast my gold without flux and had no issues. There was a light flux lining on the melting dish to prevent gold from sticking, but nothing more, and not enough to pour out with the gold. The flux was discolored light purple, the result of absorbing colloidal gold. If flux changes color when gold is melted, unless it's purple or pink, it's a sure sign the gold is not pure.

Harold

 

[DNIndustry]

Just to clarify...
I have never put borax into graphite, it was just a thought

On the graphitestores site they have hitemp coatings, but not high enough. They market and recommend them to prolong life and prevent crumbling. Per there customer service rep.

Through my use of the graphite crucible (2 of them) with heating from the bottom with a Propane.oxygen torch the graphite crumbled off inside into my button. I did preheat it and tried to "soot" it up a bit inside prior.

 

[goldsilverpro]

I'm with Harold. Never put fluxes in a graphite mold. The mold will be degraded. When I really wanted a perfect surface on a pure gold bar, I would smoke the mold with acetylene. It's not necessary, but you will get a better looking ingot.

Through my use of the graphite crucible (2 of them) with heating from the bottom with a Propane.oxygen torch the graphite crumbled off inside into my button. I did preheat it and tried to "soot" it up a bit inside prior.

Sounds like the crucible was damp.

 

[Harold_V]

On the graphitestores site they have hitemp coatings, but not high enough. They market and recommend them to prolong life and prevent crumbling. Per there customer service rep.

Refractory washes are commonly available. That's likely what they're pawning off as a mold covering. They're hardly permanent, and they are difficult to use without creating an ugly surface. I have no idea why anyone would want to use them for casting ingots unless they were huge ingots for trade in commerce. Anything presented to small investors should look like jewelry to create confidence in potential buyers. If your product looks poorly made, it likely is.

Through my use of the graphite crucible (2 of them) with heating from the bottom with a Propane.oxygen torch the graphite crumbled off inside into my button. I did preheat it and tried to "soot" it up a bit inside prior.

Ok-----I've said this more than enough times. No one in their right minds uses a mold for melting. I realize that's not what you said, but the very idea that you're using graphite is troubling to me. There is no need to use graphite when dealing with gold. If your gold is pure, it offers nothing that can't be offered by far more desirable materials.

Have you ever read my comments on melting gold with melting dishes?

If you'd like your problems to come to an end, I suggest you follow the advice I've provided. Start with NOT heating the container, but the gold instead. Do it in a clay dish, which is made to be used accordingly. Follow my instructions for preparing the dish for use, and it will serve you flawlessly for a long time. Lose the notion that you should be working with graphite.

The ingots, below, were poured in iron molds, blackened with soot from an acetylene torch, using clay melting dishes. worked for me, and worked well for years.

Harold