Smelting Gold - How easy is it?

I consider myself pretty good at most tasks. Theres not too much that I try to do where I fail but my attempt at melting our little scraps of SDC gold into an ingot was not very successful.



I started out with an old stainless steel electric kettle. I removed the lid and all the electrical components.
Then I went to Bunnings and bought a bag of Perlite potting mix. Perlite is a lightweight mineral that is crushed into about 5mm particles. Its a good heat insulation and can handle the temperatures required for a gold furnace.



The perlite is bonded with Silica Glass, a liquid that you can manufacture but I preferred to buy it online in powder form.
I made a little wooden plug the shape I wanted my ingot to end up and then used it to form the cement mould. I formed the mould in a steel shell so that even if it cracked the gold couldnt easily escape.
I decided to buy the oxy & acetylene from Bunnings because they dont charge a rental fee on the bottles. Then I found out that it was going to cost me over $500 for the deposit and gas so I looked for other ways. I connected the LPG to the cutting torch but just supplied compressed air to the oxy hose.



For the first trial run I used a couple of small lead wheel weights with a pinch of borax for flux. This ingot is just lead but I got to try the equipment.



For a real pour I started with just over an ounce of clean gold.



As you can see the flame was intense and the sound of the furnace in action was deafening.



This photo is after the flame has been turned off. The crucible and gold were glowing almost white but it was still not hot enough to melt the gold.



I ended up driving to Busselton where I could use my brothers oxy/acetylene torch to melt it.
The first pour went well but the borax I used for flux stayed firmly stuck to the crucible. I loaded the second one ounce batch with a little more borax and it soon became a molten mass that appeared transparent. I figured it might be a bit too hot to pour so I gave it a few moments to cool but that was a mistake. I don't know what caused the problem but the gold and flux solidified and wouldn't pour. Even when a lot more heat was applied it stayed solid to touch with a screwdriver.



Eventually it melted again so I parted the flux with a screwdriver and poured it. The resulting ingot came out looking more like copper than gold.



Some gold stayed in the crucible, some coated the screwdriver and perhaps there's still some in the flux.

Overall I'm not happy with my efforts so far.



My furnace was not hot enough. My second piece of gold came out looking more like copper. I lost (for now) a lot of gold in the process and messed up the crucible I'll just have to give it another go.....

Good on ya for having a crack. Better luck next time

Maybe some of your found gold has a copper content high enough to make a coloured gold like rose gold,... depending from whence it came (only suppositions on my part).

Hey Phil,
How goes it Ol' mate?!

I see you are going through the trials and tribulations that we went through many moons ago!!!
I think I still have a 50mm gal fence post cap around somewhere that I tried to use as a crucible many years ago!!!
It weighs prolly 5 grams heavier than when new.... and it wont reveal where the gold has gone!!

Mate I ended up realizing that the only way to do this properly was with a proper furnace. They aren't that dear if you look around, but don't forget to buy a couple of extra crucibles. Seriously, you wont look back mate. I reckon I lost around 2 ounces, buggering around trying to do it on the cheap!

For small amounts of fine gold, or our poverty pot, I use a Keeble block, or part thereof and MAP gas... Use a suitable drill bit or similar to form a shape for your ingot/button.

I think, I might have put up a little thread on it here years ago?? Dunno??

Anyway. use map gas, (hotter than lpg, cheaper than oxy) and 'sneak up' on your gold until you can move it around with the flame, it needs to be that white that you need your oxy welding goggles to look at it.

Preheat your mold.......hot...

DONT poke the mix with anything other than a graphite rod!! I have a pen knife and a small screw driver here that the tips are worth more than the item!

Pour accurately and promptly, the hotter the gold was, the more time you have..

Eye protection and safety at all times eh?!

Research 'Jewellers Pickle acid', you can end up getting it from a pool shop or if you know someone that kills 'crown of thorns starfish' for a living......

When the poured ingot changes colour in the mould, (very quickly, depending on the pour temp) dip it (NOT DROP IT) in the pickle, let it cool in there, then out into water...

You should get a nice ingot, the shape you wanted...

Hope this helps! Call me if you get stuck!

Simmo said:

Hey Phil,
How goes it Ol' mate?!

I see you are going through the trials and tribulations that we went through many moons ago!!!

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Hope this helps! Call me if you get stuck!

Click to expand...

Thanks Simmo for the welcome advice. "Call me if you get stuck" How many calls a day do you take??

silver said:

Maybe some of your found gold has a copper content high enough to make a coloured gold like rose gold,... depending from whence it came (only suppositions on my part).

Click to expand...

Silver, I was wondering about that. The gold coloured bar came from Meekatharra gold. The copper coloured one was poured from Leonora gold. But it will be interesting to see what happens when I try Simmo's suggestion and use Jewellers Pickle.

Make sure you fully clean the crucible before each pour as a buildup left can cause metals to stick to it
Is the color all the way through or just a coating around the pour?

AtomRat said:

Make sure you fully clean the crucible before each pour as a buildup left can cause metals to stick to it
Is the color all the way through or just a coating around the pour?

Click to expand...

AR the flux left in the crucible is set like concrete. I chipped it out but my lost gold is spread throughout.

Acid treating may be the only way to save what's left in the alloy there?

When I melted the lead my flux came out clean. It was mostly white like the borax by expanded. With the gold the flux ended up staying in the crucible like a blob of glue? It would have been very difficult to get out while the crucible was hot.

Put it in some battery acid(Sulphic acid) that should dissolve the borax.
It looks to me that you are using far to much borax,you only sprinkle the borax on the gold when it is bright colour,just before it is ready to melt.
Another cause that can lead to the problem,is if the gold is dirty and there is quartz in it.
Also if you put the acetylene flame on the gold it can blacken your gold.
I refine gold and I use a electric oven,so if you aim to melt your gold in the future you will find it easier to use one,you can find them on gumtree or Ebay secondhand at a good price,a small unit,enough to just fit he crucible in,one that that has temp to 1150c.you will get a nice clean melt.

Regards Frank

Thanks Frank I'll do a little more research. I'll upend that old battery I took out the other day as well.

Good advice there Frank...

I thought of something else too Phil..
When I tried to melt an ugly 1 or 2 ouncer with an oxy, the lad at the work shop said, 'Oi, you need a pepper box for that..."
So he brought out this 'Pepper Box' tip thingy for the oxy... Hooley Dooley, that was differant!!!
Ask your Bro if he has on of them maybe??

Hey Moneybox, you're on the right track but your procedure needs adjusting. Following is how we melt gold after refining from e-waste like computers and stuff. Gold melts at a bit over 1000c and this can be done with a butane or mapp gas bottle you can get at any good hardware. Where the following says tie your gold powder in a coffee filter, it is talking about what we have recovered from the e-waste. Doesn't matter, you can do the same with your gold pieces.

1. Carefully tie your gold powder in a coffee filter in a ball shape. Place this in a dish in Alcohol. Put this well away from your next process.
2. Now we need your blowtorch, Borax, melting crucible, and a bucket of clean water.
3. Start heating up your crucible with your torch. Use a circular motion. Keep heating for about 1/2 an hour or until every spot you touch with your flame is bright red/orange.
4. Remove the flame and sprinkle a spoonful of borax onto all surfaces of the crucible and then hit it again with your torch until the borax is clear and flowing.
5. Now add your ball of gold powder to the crucible.
6. Using your torch in a circular pattern melt the powder from the outside in. Suggest you use long nosed pliers or similar whilst melting the gold.
7. When all the gold is melted into a single gold ball, quickly pour the gold into your water bucket.

Okay, not exactly what you are trying to do by making it into a gold bar, but the above should give you a better idea of how to use the borax and how to heat up your crucible. Obviously heat is very important. Once you lose the heat, your gold will just go solid again. The alcohol I mention is the rubbing alcohol that you buy from the chemist - not what you drink!! Hope you can follow what I'm getting at.

I've never known a 'too much borax' as it just melts to its 'glass' form and you pull the gold from it still under heat. You could put 10 cups of borax onto it, pour it..wait for the borax to crack off ( or explode make sure its covered ) to reveal the metal.

I think your problem is caused by alternating temperature differences and too low heat.

Carbon helps with the process and some choose to smelt in a potatoe or on a 4x2 piece of wood, burning them to black to create the carbon.

Make sure that mold is hot too and that you melt the gold as one mass rather than forcing the metals to re crystallize when a cold bit gets added to the mix.

Great comments above, I hope it all helps for maximum recovery

WA gold has a higher copper content than Victorian gold.
I melted 8.4 grams of Victorian GT small sub gram nuggets and one side of the button came out with what looks like a copper coating though not as bad as yours?
I have since been told i should have left the furnace going with the molten gold for a few minutes longer, will be trying that when i get enough small sub grammars.

I use these crucibles with anhydrous borax along with an oxy-mapp gas set , the main thing is to line the crucible first with a liberal coating of molten borax before starting the process, so far I have had no trouble smelting fine alluvial gold.

http://www.ebay.com.au/itm/Silica-M...349463?hash=item1e89f1e1d7:g:vXcAAOSwVupTp585

Cheers

Barry

Yeah bazza, you're spot on. I know I went a bit describing what I do with e-waste, but what you say about the borax and using the oxy-mapp is it in a nutshell. Also remember to keep that heat up to everything.

If you look around the goldfields you will see at some of the old mine sites, slag from when they melted the gold,if you crush it you will find little balls of gold in the slag.
Even when you crush the slag,the gold will not adhere to mercury,because there is a coating of borax on the gold.

Regards Frank

Simmo said:

Good advice there Frank...

I thought of something else too Phil..
When I tried to melt an ugly 1 or 2 ouncer with an oxy, the lad at the work shop said, 'Oi, you need a pepper box for that..."
So he brought out this 'Pepper Box' tip thingy for the oxy... Hooley Dooley, that was differant!!!
Ask your Bro if he has on of them maybe??

Click to expand...

Ok now I've got it.

Firstly I should have heated the crucible and coated it in borax. Then I should have used Simmo's suggestion and brought out the "Pepper Box" thingy.



I guess this is what you meant Simmo. I did light it up but when it goes out it goes with a BANG and I could see my gold all spraying back to mother earth

Anyway I think these are the two main problems. A poorly prepared crucible and insufficient heat. I will work out the heat problem but I won't be using the "Pepper Box" thingy.

Thanks guys. There will be a round 2 soon.