# Graphite molds



## Dadiola (Aug 6, 2014)

Ive been using a graphite mold like this http://www.ebay.com/itm/1-oz-Gold-Bar-High-Density-Graphite-Ingot-Mold-Loaf-1-2-oz-Silver-Copper-/310939924492?pt=LH_DefaultDomain_0&hash=item486576b80c to pour my 1 oz gold bars but Ive found that I have a hard time hitting the center of the hole and I usually get bars that are somewhat deformed.

Anybody use this type mold? http://www.ebay.com/itm/1-oz-Gold-Art-Bar-Size-High-Density-Graphite-Mold-Bullion-1-2-Silver-/151370790384?pt=LH_DefaultDomain_0&hash=item233e66f5f0 Im thinking about switching to it as it looks like it would be an easier pour. My concern would be the thickness of the poured bar. Seems it may be pretty thin and bendable. Any feedback regarding the mold would be helpful.


----------



## Geo (Aug 6, 2014)

The mold would have to be very level and you would have to keep the mold heated. If the mold were too cool, the gold would harden in lumps and look really bad. 

Aside from that, I like it.


----------



## Dadiola (Aug 6, 2014)

I keep the mold heated by just leaving the prior melt in it before I pour the next...seems to work pretty good. The question is whether or not anybody else has used this type mold. I don't know how thin the bar would be.


----------



## g_axelsson (Aug 6, 2014)

1.7 mm deep..... an one ounce bar would pull together from surface tension and curl up in a button. There's no way it would fill up a thin mold like that on it's own.

Ask the seller to show a bar he poured in that mold.

Göran


----------



## Harold_V (Aug 7, 2014)

What Göran said. Thin ingots are not poured---they're rolled, blanked and then stamped (coined).

Gold won't pour thin, even if it's held at the melting point for a period of time. It balls up. That's why the buttons we see displayed are always small in diameter and thick. Beyond that, it makes no sense to have such a shallow mold. To be functional, it should be no less than ¼" deep. Mine were deeper. Also, I wouldn't trust any mold that relied on being poured full, as molten gold has a way of rising above the edges of a mold while it's being poured. In general, that's a poor design.

I fail to see the attraction to graphite molds. All of mine were cast iron and served me perfectly well for all the years I refined. That's one of the advantages of using iron for a mold. It's permanent, unlike graphite, which slowly burns away. 

Harold


----------



## Anonymous (Aug 7, 2014)

Harold. What's the process for pouring into cast iron molds please? 

Do you preheat the mold and what kind (if any) of flux is used?

Thanks in advance

Jon


----------



## Geo (Aug 7, 2014)

Jon, I haven't cast gold in iron but I have cast copper in steel molds. You need to coat the iron with soot from an incomplete combustion of a high carbon fuel like a candle or pure acetylene. They sell (or you can make your own) paste made from oil and soot or oil and graphite dust. You can paint the paste on with a brush. I made mine with peanut oil and graphite dust. If it's a large pour, it's best to pour in moving motion so you are not pouring on one spot continuously. If you pour in one spot, the molten metal will burn through the soot and may melt the iron and fuse with it.


----------



## Dadiola (Aug 7, 2014)

Thanks for the inputs. I was thinking that the mold was too thin as well. I keep hitting the sides of the mold that I currently have when I pour and I end up having to remelt the gold. Its gets irritating. 

There is no reason as to why I use graphite and not iron other than the fact that I've never seen any 1 oz iron molds. I'm just a hobbyist refining 1 oz at a time as I collect enough gold. I only have 5 one ounce bars so I'm still pretty wet behind the ears.


----------



## goldsilverpro (Aug 7, 2014)

A cavity 0.4" x 1" X .25" deep OR 0.5" X 0.8" X .25" deep in a graphite mold would hold about 1.017 troy oz of pure gold, brim full. A 1" X 2" X .5" deep mold will hold 10.17 oz of gold.

I have used both cast iron and graphite molds. I normally used graphite for the small stuff (usually 10 oz gold bars) and cast iron for the big stuff (usually 400 oz silver bars). I also used 10 and 100 oz graphite book molds for silver bars that I stamped and sold. The cast iron molds were usually coated with a thin layer of motor oil (no puddles!), using a cheap paint brush, after pre-heating and before pouring. Sometimes I used acetylene. With the graphite molds, both open and book types, I found the the surfaces of the bars were smoother and shinier when I carboned the molds with acetylene. Warning! Do not get slag on the graphite molds. At the least, a drop of slag will roughen the area it lands on.


----------



## Harold_V (Aug 7, 2014)

spaceships said:


> Do you preheat the mold and what kind (if any) of flux is used?


Depends on one's objective. 
Pouring pure silver or gold, in my opinion, requires that no flux be used. It also isn't necessary. Pouring silver that is melted cement silver I fluxed, but I used only borax. Such a pour was to a cone mold, which was preheated (to ensure no moisture was present), and blackened with mold dressing. Buttons from a cone mold are easier to process after casting. Once cleaned of flux, they were remelted and anodes poured, using no flux. 

Mold blacking is readily available from foundry supply sources, at least here in the US. It's nothing more than a thick slurry (paste) of carbon, water and perhaps traces of alcohol. It can be painted on with a brush. I used this material for my cone molds, as well as the 100 ounce mold I used for silver bars. 

For casting small bars of pure silver and gold, my procedure was to use an acetylene torch to blacken the molds. It applies a smooth covering that prevents contact of the molten metal with the iron mold, and allows for a smooth finish on the ingot, assuming the mold is preheated (I heated mine quite hot, although not hot enough to ignite the layer of applied carbon). I also poured by traversing the mold from one end to the other, to avoid the hot stream of metal penetrating the carbon layer. On more than one occasion I burned through the carbon when I failed to do so. 

You can avoid the problem of burning through the applied carbon layer by using a graphite mold, but unless they are used in an inert atmosphere, they are a poor choice, as they burn away with each pour. 

Harold


----------



## Anonymous (Aug 8, 2014)

Cheers - appreciate that.


----------

