Help with a gold melting dilemma

[Xydoman]

I'm back. I'm proud to say that with the help of members of this forum, I have sufficiently learned just a couple of the basic processes to extract and refine gold from computer parts. It's taken alot to get to this point, but I can now go from start to finish with out any hiccups or consultations... that is until my last crucible broke, and was given one of these graphite crucible from a friend... or fused silica? Not real sure. A quick description of the crucible: handling it by hand leaves what I can only assume is graphite all over my skin. Looks like pencil leas residue. The reason I say fused silica?? Is because when burned at high temperatures, these little clear beads seem to seep out of the walls of the crucible. More on these in a minute.

So I followed the instructions on preparing the crucible, which made no mention of borax or any other type of glazing. So I thought I was ready to go.
I put the refined gold powder in the crucible, add a small amount of borax and begin the melting process. So the gold DID melt, but these clear beads seeping out of the crucible have pooled up into a single puddle, and the gold seems to have spread out into a layer on top of this puddle. What's more, is tgar after a while, I figured to gold wasn't going to come together in a bead, so I stopped. Once it cooled, I realized that what I THOUGHT was gold I'm a layer on the top, ALSO contained a large amount of the graphite that the crucible is made out of, also in a layer on top of the solidified puddle. Upon further inspection, I realized that there are countless gold balls trapped within this silica like substance along with more of the graphite.i thought at that point maybe that I just needed to heat it longer to allow all of the gold balls to combine. So I did. After 1.5 bottles of Mapp gas I stopped and examined to contents of the crucible once it cooled. It has now turned into a puck, of extremely hard ... glass?? Silica?? I still don't know, and the gold and graphite seemed to have melted into the puck evenly all the way through it, turning the puck into a solid shiny Grey color, with bits of my gold poking through the surface on all sides, top and bottom. So I decided to abandon the graphite crucible and made a crucible out of a fire brick. Unfortunately this is where I compounded the issue. Now the gold has seeped into the poors of the brick, along with this graphite and silica mixture. I would like to know the best way to separate all this mess and then I'll return to my reliable ceramic crucible

 

[Golddigger76]

Scrape or chip as much gold as you can get loose and dissolve aqua regia or hydrochloric and bleach, filter until clear and drop with smb.
This time get on Amazon and get yourself a small ceramic melting dish with handle for around $15.00, heat it red hot with your torch and sprinkle a little bit of borax on it until it looks lightly glased.
You shouldn't need to add any more borax when melting.
With that being said I prefer a propane torch and have melted gold countless times with one, not the little cheap one's that looks like a silver straw with a valve on it but one that is made for brazing that puts out a real fire cone.
I have wasted a lot of gas bottles trying to melt gold and silver with cheapo torches.
I will try to get a picture posted of the propane torch that I use in a while when I get back home.

 

[Xydoman]

Yeah i know right? My main problem in tge beginning as i was screwing up batch after batch amounted to nothing more than impatience. And this is yet another issue attributed to the same thing. So it's literally encased in the Flux and buried in the pores of the brick. I thought about cutting the portion of the brick containing it and grinding it up, the dissolving it again to separate it from the graphite.. but I'm unsure of what affect aqua Regia has on graphite. I guess that should've been my question.. in the pics, if u look closely, you can see a couple of nice sized buttons in the pores, along with tons of tiny little gold dots that were unable to join the bigger pool I would reckon due to the terrain of the makeshift crucible. I feel like an ***** because I happen to know that tge gold typically pools up in the lowest point in tge crucible, and I now surmise, that this pooling up action is facilitated by the flow characteristics of the Flux pool. And I literally just realized this last part. So it would make sense that if heated longer , it would separate from the graphite as long as I stayed away from tge graphite crucible.. am I correct here?

 

[andu]

I know metal can be left behind in graphite, so perhaps after you scrape the gold out could also get a bit of the graphite (the most exterior side) and try to pass it thru a bit of AR.

 

[olawlor]

... So it's literally encased in the Flux and buried in the pores of the brick. I thought about cutting the portion of the brick containing it and grinding it up, the dissolving it again to separate it ...

Your pumice-like white crucible looks like a lightweight insulating firebrick to me, not graphite. Borax flux will dissolve the aluminosilicates in firebrick to make a clear borosilicate glass, so chipping out your values will be more reliable than trying to dissolve the glass off chemically. Gold is ductile and glass isn't, so careful crushing might release the beads.

Actual graphite is a uniform, dense, slightly shiny black color. If you can find a chunk you can drill or saw it about like wood (though graphite "sawdust" is pitch black and very messy!). A big advantage of graphite is that fluxes do not dissolve it, and metals do not wet it, though I've still had dirty melts glued into the crucible with borax after melting.

To keep the heat up with a propane or MAPP torch I found ceramic blanket was much better at holding heat in than any variant of firebrick. You also want insulation all around the crucible, since losses from radiation are substantial, and it's still a near thing to get a reasonable amount of metal melted. By contrast, I found an oxyacetylene torch has enough concentrated heat to not require any insulation, at least for melting a few grams worth of precious metals.

 

[J.Najam]

Yes. Please find below.

Laziness can sometimes be a blessing too.. I wanted to clean this crucible with the dilute sulfuric solution as suggested by @BlackLabel, but instead of hopping to the market to fetch some sulfuric, I tried this little cleaning experiment with a 50Ml 5M citric acid (aq) solution. It worked great. I dipped theb crucible in a 100 ml beaker and poured the solution over it slowly and instantly there was a reaction. I dont know what caused it to do so. But here we are 45 minutes later... With frequent swirls of the beaker throughout and observing carefully if any more was needed. I added the solution in parts, like 30 Ml then 10 then 10. It worked magic. This process detached the borax and dissolved some of it though not all... But unfortunately there was no gold under there. Maybe a tiny speck that I couldn't see, I wasn't too sure of it.

Hello,

I dont know if this helps you, but you can find the condition of my crucible before and after the treatment. You may go through the above posts and see if it helps you liberate your gold off your dish.

 

[Deano]

All crucibles, including graphite, will be eroded by the presence of borax in the smelt.
If they were not eroded you would just buy one crucible for a lifetime of smelting and the suppliers of crucibles would go out of business.
Formation of multiple small beads in a smelt is caused by coatings of base metals in place on the gold before smelting starts.
These can be eliminated by simmering the unsmelted gold in 20% HCl for a few hours before filtering, drying and smelting.
The simmering time is dependent on the types and levels of base metals present.
After the simmering treatment the gold can be smelted without flux present.
Deano

 

[Ultrax]

I'm back. I'm proud to say that with the help of members of this forum, I have sufficiently learned just a couple of the basic processes to extract and refine gold from computer parts. It's taken alot to get to this point, but I can now go from start to finish with out any hiccups or consultations... that is until my last crucible broke, and was given one of these graphite crucible from a friend... or fused silica? Not real sure. A quick description of the crucible: handling it by hand leaves what I can only assume is graphite all over my skin. Looks like pencil leas residue. The reason I say fused silica?? Is because when burned at high temperatures, these little clear beads seem to seep out of the walls of the crucible. More on these in a minute.

So I followed the instructions on preparing the crucible, which made no mention of borax or any other type of glazing. So I thought I was ready to go.
I put the refined gold powder in the crucible, add a small amount of borax and begin the melting process. So the gold DID melt, but these clear beads seeping out of the crucible have pooled up into a single puddle, and the gold seems to have spread out into a layer on top of this puddle. What's more, is tgar after a while, I figured to gold wasn't going to come together in a bead, so I stopped. Once it cooled, I realized that what I THOUGHT was gold I'm a layer on the top, ALSO contained a large amount of the graphite that the crucible is made out of, also in a layer on top of the solidified puddle. Upon further inspection, I realized that there are countless gold balls trapped within this silica like substance along with more of the graphite.i thought at that point maybe that I just needed to heat it longer to allow all of the gold balls to combine. So I did. After 1.5 bottles of Mapp gas I stopped and examined to contents of the crucible once it cooled. It has now turned into a puck, of extremely hard ... glass?? Silica?? I still don't know, and the gold and graphite seemed to have melted into the puck evenly all the way through it, turning the puck into a solid shiny Grey color, with bits of my gold poking through the surface on all sides, top and bottom. So I decided to abandon the graphite crucible and made a crucible out of a fire brick. Unfortunately this is where I compounded the issue. Now the gold has seeped into the poors of the brick, along with this graphite and silica mixture. I would like to know the best way to separate all this mess and then I'll return to my reliable ceramic crucible

You have too many impurities in your gold. To save your gold just remelt your resulting substance with 10x quantity of lead. But slowly(!), the best way is the muffle, and do not use MAPP and do not overheat the melt (temp. should be about 900-1000C, not more), lead should have enough time to dissolve small gold beads from your borax chunk (20-30 minutes). You can also add 5-10 grams of 100% dry NaOH to the melt to improve its fluidity. After that just dissolve the lead button in nitric acid and you will receive all your gold.

 

[Ultrax]

I found an oxyacetylene torch has enough concentrated heat to not require any insulation, at least for melting a few grams worth of precious metals.

Usually, it is difficult to control the temperature with an acetylene torch, so the melt is greatly overheated, and significant amounts of gold evaporate(!). Due to the high speed and temperature of more than 3000C gas flow, part of the gold is also blown out of the melt towards the burning torch. An acetylene torch gives a high melting speed, but unfortunately also large losses of precious metals.

 

[orvi]

Usually, it is difficult to control the temperature with an acetylene torch, so the melt is greatly overheated, and significant amounts of gold evaporate(!). Due to the high speed and temperature of more than 3000C gas flow, part of the gold is also blown out of the melt towards the burning torch. An acetylene torch gives a high melting speed, but unfortunately also large losses of precious metals.

Any oxy/fuel torch is relatively harsh and do evaporate metal. Most easily silver. Even classic propane/air torches can evaporate silver from the melt, altough it is not very significant.

When I use oxy/propane to melt gold or other metals, I start with reducing flame (just enough oxygen to prevent formation of soot), and gradually add oxygen to the point I obtain good power to start melting the charge. I then hold it in this setting to fully liquify the melt, and that´s it. Going full combustion (balanced mixture of fuel and oxygen) with highest power from the start often result in harsh losses, if you are dealing with smaller quantity of material. Simultaneously poisoning yourself with metal vapors.

Good indicator is when you take the torch and point it on mineral wool insulation. Judging by the glow of the wool, and speed of melting a hole in it ( ) you can assume where you´re sitting with the temperature.

This is also the best ballpark technique to optimize oxy/fuel ratio to give you the highest power out of the torch. If you are using oxygen concentrator (as I am), this way, you can very easily max out power output, as you have definite max flow of oxygen dictated by the machine.

 

[Hartbar]

I found glazing a fused silica melting dish to be quite an art.
If you do it properly, it will look same color as before, but have a shiny glaze like a white teacup.
After melting and pouring AU, it will take on a purple color and always have some tiny gold beads mixed in, you have to glaze to and over the pouring spout.

 

[J.Najam]

I found glazing a fused silica melting dish to be quite an art.
If you do it properly, it will look same color as before, but have a shiny glaze like a white teacup.
After melting and pouring AU, it will take on a purple color and always have some tiny gold beads mixed in, you have to glaze to and over the pouring spout.

I have been trying to do this for quite sometime now to be honest with a butane torch. I even ordered a nichrome wire to catalyze the fire but I just don't know what technique I'm going wrong with here. It just won't glaze. Had it on for 45 minutes or so on multiple spots but nope, it just won't...

 

[Yggdrasil]

I have been trying to do this for quite sometime now to be honest with a butane torch. I even ordered a nichrome wire to catalyze the fire but I just don't know what technique I'm going wrong with here. It just won't glaze. Had it on for 45 minutes or so on multiple spots but nope, it just won't...

Heat it to a dull red and sprinkle the borax on this spot, heat it more on the same part and move/roll the melting dish back and forth so the borax flows and covers the part evenly.
Then move the torch a bit and repeat until the entire inside is covered.
There is Youtube videos showing the technique if memory serves me right.

 

[J.Najam]

You're absolutely right about everything. But I don't understand why it won't just melt the borax down? All the videos I see, I just don't know why it won't work for me the same way.

Notice how the borax is stuck onto it but doesn't really melt down

Heat it to a dull red

It actually became bright orange and still didn't...

 

[Yggdrasil]

You're absolutely right about everything. But I don't understand why it won't just melt the borax down? All the videos I see, I just don't know why it won't work for me the same way.

Notice how the borax is stuck onto it but doesn't really melt down

It actually became bright orange and still didn't...

Why is it blackened?
And are you sure it is proper dehydrated Borax?

 

[J.Najam]

Why is it blackened?
And are you sure it is proper dehydrated Borax?

I'm not sure about that, maybe it was too moist outside when I was carrying out this process. The jar containing the borax had a little bit of a mist on the inside too if I remember it correctly.

How do you dehydrate borax by the way? Or is it supposed to arrive dehydrated..?

 

[Yggdrasil]

I'm not sure about that, maybe it was too moist outside when I was carrying out this process. The jar containing the borax had a little bit of a mist on the inside too if I remember it correctly.

How do you dehydrate borax by the way? Or is it supposed to arrive dehydrated..?

Depending on what you bought, it is either anhydrous or not.
If it boils up in foam before collapsing it is not anhydrous.
It can still be used, but you need much more.
Try using a pepper or salt box for the table to sprinkle it on the hot dish.
(Do not ever use it outside the lab again though, anything used in the lab belongs in the lab forever.)

 

[J.Najam]

If it boils up in foam before collapsing it is not anhydrous.

I didn't notice this happening, so maybe it was anhydrous but it is still possible that the container got moistened overtime.

It can still be used, but you need much more.

And yes agree to this, Going to try it out before actually trying to glaze it in my furnace. The only option left to be honest.

Try using a pepper or salt box for the table to sprinkle it on the hot dish.

pepper or salt box? sorry didn't get this. What should I be looking for in this process?

 

[Yggdrasil]

I didn't notice this happening, so maybe it was anhydrous but it is still possible that the container got moistened overtime.

And yes agree to this, Going to try it out before actually trying to glaze it in my furnace. The only option left to be honest.

pepper or salt box? sorry didn't get this. What should I be looking for in this process?

Salt/Pepper canister so you easily can sprinkle it on the glowing surface of the melting dish.

 

[Hartbar]

Sreetips has a video I think, just sprinkles tiny pinches into hot dish and melts bit by bit.
I tried the salt pepper way but had less control