# HOW TO CAST 1KG GOLD BAR



## hrushi (Feb 3, 2012)

I REFINE GOLD BY inquartation AS 100% GOLD IS RECOVERED EVERY TIME NO GOLD IS WASTED(TEMPORARILY) AT END OF EVERY BATCH I GET ALL GOLD.
I USE SS316 VESSEL AS REACTOR. I USE SS REACTOR AS IT IS BETTER THAN GLASS AS IT WONT CRACK.
OFTEN I DONT GET COLOR OF 9950 1KG GOLD BAR. MANY TIMES THERE IS RED COLOR SKIN OR LAYER ON THE METAL. HOW TO REMOVE IT.
SECONDLY HOW IS 1KG GOLD BAR IS CASTED. OF WHAT MATERIAL DIE IS MADE OF??
I THINK DIE IS MADE OF SOME CARBON MATERIAL.
REGARDS
HRUSHI


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## Geo (Feb 3, 2012)

please dont post using all CAPS as it is considered shouting and therefore considered rude. molten gold should never come into contact with other metal (even stainless steel). the best material for casting gold ingots is carbon graphite molds.


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## hrushi (Feb 3, 2012)

Geo said:


> please dont post using all CAPS as it is considered shouting and therefore considered rude. molten gold should never come into contact with other metal (even stainless steel). the best material for casting gold ingots is carbon graphite molds.


extremly sorry for all caps  
and how do i get good color without doing AR process :?:


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## publius (Feb 3, 2012)

hrushi said:


> Snip... and how do i get good color without doing AR process :?:


Do a forum search for Acid/Clorox procedure. Also download and read CM Hole's book. You will find links to it in many of the forum members signatures.


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## kdaddy (Feb 3, 2012)

It sounds like you are inquarting, dissolving in nitric, then melting the undissolved material. If this is what you are doing your gold still has impurities, red is most likely copper. There are no shortcuts if you want good purity, AR is your friend.


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## Claudie (Feb 3, 2012)

When dealing with an amount as small as 1 gram, maybe the best way would be to roll the Gold out flat, then use a proper size punch to knock out a planchet. Just a thought. :|


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## philddreamer (Feb 3, 2012)

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=61&t=9982&p=96025&hilit=melting+gold#p96025

I hope this helps some!

Phil


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## hrushi (Feb 4, 2012)

kdaddy said:


> It sounds like you are inquarting, dissolving in nitric, then melting the undissolved material. If this is what you are doing your gold still has impurities, red is most likely copper. There are no shortcuts if you want good purity, AR is your friend.



I have checked purity on XRF and spectrophotometer it ranges from 99.74% to 99.96%.
thing that you have boil it minimum 2 times in nitric acid after 1 reaction is complete.
I am sure you will achive purity.
if you do reaction in glass beaker you would get very nice color of gold as well
there are two disadvantage of this process
1. lot of Ag is required and again we have to recover Ag.
2. if reaction is done in SS vessel gold gets some kind of red color on top of gold and id ammonium chloride that red color goes as well to some extent but you dont get 1kg 99.50 gold bar color.

thanks
hrushi


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## Geo (Feb 4, 2012)

my guess would be iron from the SS. stainless steel has a resistance to attack from nitric but when you heat the nitric it will attack the stainless to some degree. high grade stainless steel is passivated in nitric by a layer of oxidized (nickle?) preventing attack further at lower temperatures. since nickle is greenish-blue while iron is red, i would say its iron. you cant just clean the outside of the gold and it will be gone as the contamination will be throughout the entire melt.


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## nickvc (Feb 4, 2012)

You could try washing your gold powder through hot hydrochloric so long as you rinse it well with water only a little of the value could dissolve and it could be tested using stannous, this might remove some of the contaminants but obviously you would have to use something other than stainless preferably glass.


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## qst42know (Feb 4, 2012)

How many times have you used the same silver to inquart? 

It is possible it has accumulated enough contaminants to be less than effective.

Inquarting as the sole means of refining seems a common short cut in India. Is there a reason you don't finish the job of refining with aqua regia?


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## kdaddy (Feb 4, 2012)

I dosen't matter what the XRF results are, if you have oxides on your melt you have impurities. Have an assay done and you will see how accurate the XRF is. Why would anyone go through all the trouble to inquart just to half ass the job at the end?
P.S. Get rid of the SS and get some glass.


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## HAuCl4 (Feb 4, 2012)

hrushi said:


> kdaddy said:
> 
> 
> > It sounds like you are inquarting, dissolving in nitric, then melting the undissolved material. If this is what you are doing your gold still has impurities, red is most likely copper. There are no shortcuts if you want good purity, AR is your friend.
> ...


Courtesy of 4metals: Flux to get approx. ~9995 gold after silver inquarting + nitric.

This is the formulation for the flux to scavenge silver and base metals.

Gold Melting Flux
This is for gold from the nitric parting process

2 pounds Anhydrous borax glass (no waters)
1 pound Soda Ash
1 pound Diatomaceous earth (silica)
1 pound Manganese Dioxide
¼ pound Flurospar (calcium fluoride)
¼ pound Calcium oxide (CaO, Lime, Type S, Unslaked)

Premix all of the ingredients and store it in a closed container. It is anhydrous and will pick up moisture from the air which will make it spit. 

Add equal volume of gold sponge to flux and premix before melting.

**********************************************
How to make and stamp a 1 Kilo gold bar. Courtesy of Chloroauric Acid :

1-Weight exactly 1001 grams of pure gold (~9995 from above procedure) in pellet / shot form.
2-Melt it WITHOUT borax or any other flux in a silicon carbide or graphite crucible (that is used only for pure gold), reach a good 1,200 C.
3-Pour it in a preheated graphite mold (that is used only for pure gold). Maintain a propane torch flame on top till it solidifies.
4-Mark it with an hydraulic press (made with an hydraulic car jack) and a steel stamp with your seal, and whatever markings you want.
5-Weight the bar in an accurate balance, and file off less than~1 gram from it, till the weight is 1000.5 grams +/-. :lol:
**********************************************
Your process is fine. Glass with nitric parting is for amateurs.


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## samuel-a (Feb 4, 2012)

HAuCl4 said:


> Courtesy of 4metals: Flux to get approx. ~9995 gold after silver inquarting + nitric.
> 
> This is the formulation for the flux to scavenge silver and base metals.
> 
> ...



I agree with the above. 
304L or 304 SS reactor is a very worthy choice for nitric digestion. 
Naturally, SS corrode. the lower the concentration of the acid the faster it corrode.
The corrosion rate of 304L and 304 according to BSSA is 0.1mm per year at 40% concentration and at 110C....

That means, 0.1mm will corrode over a year if the reactor would work 24/7 at 110C... that's the way i understand it.

You should consider adding overhead stirring (vigorous) to your reactor or produce very small beads to leach (search "atomizer" here on the forum).
This way, you will expose more surface to the acid.


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## hrushi (Feb 5, 2012)

nickvc said:


> You could try washing your gold powder through hot hydrochloric so long as you rinse it well with water only a little of the value could dissolve and it could be tested using stannous, this might remove some of the contaminants but obviously you would have to use something other than stainless preferably glass.


this worked for me I took 50ml of HCL added to 500 ml water and risen gold sand and after wards I added SMB so that if any gold dissolved in HCl will precipitate. And color which I got was also good with nice shine. if i would had done this one more time color of gold would be like 9950 1kg bar. shine was also good.
regards
hrushi


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## hrushi (Feb 5, 2012)

qst42know said:


> How many times have you used the same silver to inquart?
> 
> It is possible it has accumulated enough contaminants to be less than effective.
> 
> Inquarting as the sole means of refining seems a common short cut in India. Is there a reason you don't finish the job of refining with aqua regia?



Silver can be used again n again no problem.
reason to use this process is all gold is recovered at end of every process. even if u have 5 kg of gold it can be refined in max 4 hours all metal out and melted.
no fear of Aucl be wasted (no gold is wasted)
only drawback lot of silver is required.
regards
hrushi


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## hrushi (Feb 5, 2012)

kdaddy said:


> I dosen't matter what the XRF results are, if you have oxides on your melt you have impurities. Have an assay done and you will see how accurate the XRF is. Why would anyone go through all the trouble to inquart just to half ass the job at the end?
> P.S. Get rid of the SS and get some glass.



the only reason In use SS instead of glass is it wont break or there wont be any damage. 
hrushi


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## hrushi (Feb 5, 2012)

samuel-a said:


> HAuCl4 said:
> 
> 
> > Courtesy of 4metals: Flux to get approx. ~9995 gold after silver inquarting + nitric.
> ...



Is there any metal which can be used instead of SS
hrushi


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## hrushi (Feb 5, 2012)

HAuCl4 said:


> hrushi said:
> 
> 
> > kdaddy said:
> ...



thank you 
I will try and post my reply
hrushi


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## Dr. Poe (Feb 5, 2012)

In jewelry casting, the reddish surface coat is due to traces of copper contamination. The copper oxide is polished away with fine grit on a buffing wheel. In the South African Rand, ingots of gold are polished by a large flame from a torch immediately after pouring (while the ingot is still hot). The inner part of the flame is a reducing flame and robs the trace copper oxide of it's oxygen (removing the red hue). Sometimes the simplest answers are the best. Regards; Dr. Poe 8)


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## hrushi (Feb 5, 2012)

Dr. Poe said:


> In jewelry casting, the reddish surface coat is due to traces of copper contamination. The copper oxide is polished away with fine grit on a buffing wheel. In the South African Rand, ingots of gold are polished by a large flame from a torch immediately after pouring (while the ingot is still hot). The inner part of the flame is a reducing flame and robs the trace copper oxide of it's oxygen (removing the red hue). Sometimes the simplest answers are the best. Regards; Dr. Poe 8)



Which gas is used oxygen, propane, argon, or nitrogen??
can u elaborate more
hrushi


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## hrushi (Feb 5, 2012)

some video i saw some white colored crucibles what are those made of
hrushi


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## HAuCl4 (Feb 5, 2012)

Dr. Poe said:


> In jewelry casting, the reddish surface coat is due to traces of copper contamination. The copper oxide is polished away with fine grit on a buffing wheel. In the South African Rand, ingots of gold are polished by a large flame from a torch immediately after pouring (while the ingot is still hot). The inner part of the flame is a reducing flame and robs the trace copper oxide of it's oxygen (removing the red hue). Sometimes the simplest answers are the best. Regards; Dr. Poe 8)


Aside of the two small facts that the Rand refines gold to 9999+ and that the torch flame is used for surface finish and not for color, you'd be correct: The simplest answers are the best, sometimes.
http://www.youtube.com/watch?v=nQ37SFKahc0&feature=related


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## 4metals (Feb 5, 2012)

Another option for removing the red color is to flux it off while molten using niter. If, while looking into the molten pool of fine gold, you see a haze on the surface of the molten gold, add a pinch of borax and when it settles to the wall of the clean crucible add a pinch of niter. The niter will react with the copper and it will bounce around the surface of the melt forming an oxide which will eventually stick to the small sticky spot made by the borax and then it won't pour out with the gold. 

In the older text's they refer to this process as toughening.


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## lazersteve (Feb 5, 2012)

I use this same process 4Metals mentions and it works great for clairfying the last bits of contamination from gold before casting.

Be sure not to over do the niter or you may end up with your gold spitting out of the dish if it is very dirty. A little extra borax helps prevent this.

Also make sure your gold is fully molten before adding any niter.

Thanks for this tip 4Metals, I've really grown used to using it.

Steve


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## Dr. Poe (Feb 5, 2012)

HAuCl4 said:


> Dr. Poe said:
> 
> 
> > In jewelry casting, the reddish surface coat is due to traces of copper contamination. The copper oxide is polished away with fine grit on a buffing wheel. In the South African Rand, ingots of gold are polished by a large flame from a torch immediately after pouring (while the ingot is still hot). The inner part of the flame is a reducing flame and robs the trace copper oxide of it's oxygen (removing the red hue). Sometimes the simplest answers are the best. Regards; Dr. Poe 8)
> ...


Actually I was referring to the almost single molecular thickness on the surface and of a copper contamination of less than one part in ten thousand. Having pure gold with minute surface discoloration is certainly not a new thing for me or any manufacturing jeweler. Yet, if it doesn't easily polish off, then it should be refined again. Regards; Dr. Poe 8)


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## Dr. Poe (Feb 5, 2012)

hrushi said:


> Dr. Poe said:
> 
> 
> > In jewelry casting, the reddish surface coat is due to traces of copper contamination. The copper oxide is polished away with fine grit on a buffing wheel. In the South African Rand, ingots of gold are polished by a large flame from a torch immediately after pouring (while the ingot is still hot). The inner part of the flame is a reducing flame and robs the trace copper oxide of it's oxygen (removing the red hue). Sometimes the simplest answers are the best. Regards; Dr. Poe 8)
> ...


I'm not sure what fuel they use, but I know that it is bottled and not smokey (most likely it's propane). The fuel is burned with oxygen. Swest. sells a flux guaranteed to eliminate red or pink gold. I think it might be a mixture of anhydrous borax and potassium bisulfate. Dr. Poe 8)


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## Dr. Poe (Feb 5, 2012)

hrushi said:


> some video i saw some white colored crucibles what are those made of
> hrushi


I've seen off white crucibles of either clay or zirconium oxide. The zirconium crucibles are often mixed with silicon carbide, a gray to black color. Clay crucibles are made to be used once, then thrown away. I've gotten several melts from some of them, as much a eight times. Zirconium crucibles have a relatively short 'life span' compared to the silicon carbide. The silicon carbide is my favorite. Dr. Poe 8)


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## hrushi (Feb 6, 2012)

what is difference between silicon carbide and graphite
which mold or die is better considering durability
hrushi


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## HAuCl4 (Feb 6, 2012)

hrushi said:


> what is difference between silicon carbide and graphite
> which mold or die is better considering durability
> hrushi


Silicon carbide for crucibles, and cast iron for molds. Watch the video of the Rand refinery a dozen times. Did you notice the wash in HCl after the ingot is cast?.
Graphite molds give very good finish, but they wear out fast. If you can make them yourself cheaply they are a good alternative.


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## vegaswinner (Feb 6, 2012)

How would one go about obtaining niter? I googled the term and read the wiki, i'm getting the impression it is gun powder of sorts? Is it a salt we can make by doing some chemistry with nitric or just slice open a firework?


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## samuel-a (Feb 6, 2012)

niter = Potassium nitrate (KNO3). Easily obtained as fertilizer.


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## 4metals (Feb 6, 2012)

Considering the purpose of the niter is to clean up some gold which is a little contaminated to begin with, I would resist using anything less than technical grade niter. (potassium nitrate)

God only knows what else is in fertilizer grade chemicals.


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## samuel-a (Feb 6, 2012)

good point.


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## vegaswinner (Feb 6, 2012)

Is the addition of niter something which would be recommended for every melt or is there a more specific circumstance for its use. For example, if I am stripping finger foils with ap then copper is the main base metal of concern and something I would go to great lengths to clean off before dissolution of the foils and melting of powder. If I was silver inquarting followed by nitric then copper may not be the main concern although It may still be a mild contaminant.


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## lazersteve (Feb 6, 2012)

The clean up of gold in molten form is sometimes required when trace impurities make it past your washing and cleaning processes on the powder.

In lieu of refining the brown powder a second or third time you can quickly clean the molten gold of trace impurities using molten borax and niter. 

If the brown powder melts with a clean surface to begin with there is no need to use the borax/niter cleaning process on it, so don't make it a habt of always adding borax and niter to your melts, use only when needed.

The surface of molten gold should look green and clean all the way across the surface of the molten pool. If you pull your torch away for a short moment and see what looks like floating debris, colored rainbows, or swirling patterns in/on the molten gold, then proceed to use the cleaning procedure.

This process will not remove silver contamination from gold. For silver contamination you will need to refine a second time and properly rid the powder of silver in the wash/cleanup phase or in the filtration cycle using iced solutions. 

Steve


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## Geo (Feb 6, 2012)

how toxic is the smoke produced? is it as bad as NOx?


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## 4metals (Feb 6, 2012)

On the 1st page of this thread HAuCl posted a formulation for flux using Manganese Dioxide. In addition to scavenging silver it will scavenge copper. If you are bent on melting the foils to scavenge copper try this flux. 

Since foils are from electroplating, they are high purity with possible surface contamination from the under-plating. I would be leaching in nitric to clean it up. 

Considering you plan on refining it further I would try running it in aqua regia without a leach or melt/flux. The thin foils will dissolve quickly and a small amount of base metal will not hinder you from dropping high purity gold from the solution.


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## lazersteve (Feb 6, 2012)

Great information about the manganese dioxide removing silver, I was not aware of this one. I'll have to remember this when I melt and suspect silver contamination.

Thank you!

Does the silver get removed via vaporization or does it report in the slag as another silver compound?

Steve


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## 4metals (Feb 7, 2012)

The silver will be in the slag. I usually mix it in with the payable sweeps from crucible scrapings.


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## HAuCl4 (Feb 7, 2012)

For every $1 Million in gold that you refine, there will be about $50 in silver in the slags, at today's prices. I don't know what the compound is, maybe a composite oxide of silver and manganese?. :?:


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## hrushi (Feb 8, 2012)

Now most issues are solved regarding color and mold.
what is dimension of standard 1Kg bar and top edges 

hrushi


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## 4metals (Feb 8, 2012)

The curves you point out on the bar edges are from the surface tension of the molten gold in the furnace, much like a drop of water has a curve to it. These bars have it too and the molds have straight sides, the bottom edges are square from the weight of the gold pushing into the corners.


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## its-all-a-lie (Feb 8, 2012)

That is beautiful!


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## hrushi (Feb 10, 2012)

4metals said:


> The curves you point out on the bar edges are from the surface tension of the molten gold in the furnace, much like a drop of water has a curve to it. These bars have it too and the molds have straight sides, the bottom edges are square from the weight of the gold pushing into the corners.



Nice pic.
Have you made these bars. :?: 
I have gas fired and coal fired furnace how to make these bars on them
hrushi


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## 4metals (Feb 10, 2012)

These bars were made in an atmospheric gas furnace. They are beautiful bars but come at a price the equipment is costly both to buy and operate. 

The best you can do with your equipment is to pour your bar and with a hand torch heat the bar to prolong the cooling, that will give you the smoothest finish you can get without costly equipment.


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## HAuCl4 (Feb 10, 2012)

Could you please post a few pictures of your coal fired furnace and the air injector (if any)?.


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## its-all-a-lie (Feb 10, 2012)

did i mention those bars are beautiful?


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## hrushi (Feb 26, 2012)

Try his to get those round edges 
I thin gas used is CO2 
What I did is I took mold and applied some carbon on it and got those curves
Take Kerosene lamp and hold mold on flame it will blacken all the mold just see the change(inside of mols should be darken i.e carbon should be deposited on inner surface of the mold)
I tried this many times and got desired result

hrushi


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## sasi4gold (Mar 20, 2020)

> Graphite molds give very good finish, but they wear out fast. If you can make them yourself cheaply they are a good alternative.


how to produce Graphite molds ?
Thanks 
sasi


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## Lou (Mar 20, 2020)

Buy high grade EDM graphite (I like POCO, it lasts for every, very tight grain, glass finish on bars).


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## Tarzan Tsui (Feb 25, 2021)

sasi4gold said:


> > Graphite molds give very good finish, but they wear out fast. If you can make them yourself cheaply they are a good alternative.
> 
> 
> how to produce Graphite molds ?
> ...



Graphite molds are machined out with the machine tool. You can see the video I uploaded on Youtube about graphite machining, the link is https://www.youtube.com/watch?v=fwLKI0lwqxk.
The machining process is basically like that. But the graphite material on the video is extruded graphite. For ingot molds for gold, the graphite should be molded graphite or isomolded graphite.


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