Melting Gold

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Melting Gold

Post  phill on Fri Oct 07, 2011 7:02 pm

Finaly after much procrastination, deliberation and debate I decided today that I might have another go at melting down some raw prouduct....
I did try this once before about a year ago and managed to come away with a nice gold plated ladel, message to self, don't try it in a metal ladel again!
So having aquired a proper cruicible and some borax for flux, thought I should try again.
Pieces that went into the pot were all small "fines" (like gold dirt..) and other bits were small dirty honeycombe shreds of up to about 3gms. Some of this stuff I've had sitting in Ali-brite for months (at least 6) I'm sure.
Tried at first with a small propane torch but this was only just able to melt the borax, so I got the oxy- aceyetelene torch out..... that fixed it









All in all, quite happy with the result, uh um, this time...

Phill Smile


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Re: Melting Gold

Post  HOBO'S Gold on Fri Oct 07, 2011 8:32 pm

Mapp gas works good too if you don't want the expense of oxy- acetylene gas bottles etc. a Mapp gas torch kit with disposable bottle costs around $100

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Re: Melting Gold

Post  geof_junk on Fri Oct 07, 2011 8:58 pm

I did this with propane cans on a fire brick but did find it hard to melt went the amount got larger.


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Re: Melting Gold

Post  Guest on Fri Oct 07, 2011 9:29 pm

Geoff, what is your criteria for what gets melted down and what doesn't?

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Re: Melting Gold

Post  geof_junk on Fri Oct 07, 2011 9:48 pm

Byteman wrote:Geoff, what is your criteria for what gets melted down and what doesn't?

Basically poor specimen and and panned gold that go to the refiners.

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Re: Melting Gold

Post  Guest on Fri Oct 07, 2011 10:11 pm

Thanks Geoff, though I have no idea what is considered a poor specimen.

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Re: Melting Gold

Post  Guest on Fri Oct 07, 2011 11:06 pm

Good job Phill. The old oxy set works a treat, the map gas torch would be ok for a one off job, to many dollars for such a short amount of heat!

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Re: Melting Gold

Post  dryblower on Sat Oct 08, 2011 10:16 am

Does anyone know of a supplier of pure borax ?
I found the Bunnings borax didn't come out of the crucible as well as the old crystalised borax I got yonks ago.
Maybe I didnt use enough for the ( small ) amount of impurities in the dollied gold , but I havent had this problem before.
The gold still pored out ok , but the slag trapped a lot of prills of gold because of its high viscosity.
I use a LPG gas powered furnace .
Cheers
DB

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Re: Melting Gold

Post  opalngold on Sat Oct 08, 2011 11:05 am

Having similar trouble as Dryblower , how do you remove the remains of the borax and crap [ slag ] left over in the crucible after melting ? If it’s left in there it seams to soak up too much heat. Tried chiselling it out that did work but also chipped the crucible. Any ideas? I use Mapp gas. Thanks Greg
PS Geof junk I don’t know how you got enough heat using propane?


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Re: Melting Gold

Post  dryblower on Sat Oct 08, 2011 2:56 pm

Hi opalngold.
I always have had small bits of slag leaft stuck to the crucible walls after a pour , but in a graphite crucible they chip out fairly easy or I usually just leave them there for the next time. The last pour with the bunnings borax I had trouble getting any slag out and even after a bit of shaking and curseing only half of it droped out , the rest stuck in a lump on the side of the crucible. The furnace will get the temp way over gold melt ( 1100 deg C ? ) so most of the slag usually runs out into the mold . Looking at the borax container it says there is 980g of borax in the 1000g , but doesnt say what the other 20g are ? . Maybe the small lumps of melted rock stick to the crucible and wont slip out like the borax slag should ?
Cheers
DB

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Re: Melting Gold

Post  Guest on Sat Oct 08, 2011 8:33 pm

I always found the local Chemist can supply all your needs, if not they know who to get it from!
Biggest problems I ever incurred was the temp. You really need to be as close on the money as possible? Hard task! but not impossible. affraid

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Re: Melting Gold

Post  chopppacalamari on Sat Oct 08, 2011 10:13 pm

Your local chemist will have borax powder. It is supposed to stick to the crucible. I heat my crucibles up and pick out the biggest bits of slag with titanium tweezers and just leave the little stuff. If you end up with too much in there and its all dark there are two ways I clean mine up. get it orange hot and (wearing a heat proof glove) scrape it with the blunt end of the tweezers into a pile and scoop it out like margarine on a knife.

The other way to clean it out is to add salt to your crucible. With heat it goes runny and turns the borax into a really runny clear slurry that you can just pour out if you keep the heat on it. It will clear the crap out of your crucible too. the problem is you can't get all the salt out so your next pour will have salt on top of it which creats a tiny amount of pitting. The ultrasonic will take all the salt off and it wont make much difference unless you're trying to pour an even bar for making jewellery or something like that. The stuff you pour out of the crucible will have all the tiny bits of gold slurry in it and you can throw the whole lot in for the refiners.

I find by the time I think I need salt, the crucible has a few cracks in it and I just throw the whole thing in for the refiner and start on a new one. Your crucible will last longer if you melt borax into it before you do your meltdown.

Dicko.

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Re: Melting Gold

Post  dryblower on Sun Oct 09, 2011 9:38 am

Cheers someday and chopper for the tips , will give the chemists a try . Also the salt in the crucible is worth a try
I havent had any cracking problems with graphite crucibles , mine tend to flake away and get a bit thin after many uses.
One thing I found with my furnace is a small 12v fan behind the burner forceing more air in helps the gas burn completely which raises the furnace temp and speeds up the melt .
A spot temperature check gun would be handy , but they are a bit pricey I think .
I thinly coat the steel mold with moly disulphide grease to prevent the gold sticking to it , and preheat it a bit before use .
The slag I dolly up and pan the prills out for next time.
DB

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Re: Melting Gold

Post  opalngold on Sun Oct 09, 2011 5:49 pm

I had another crack at melting some gold today, cleaned the crucible first by heating the black slag till molten then scrapping it out with a carbon rod also removed more slag during the melting process, worked well. I had to use quite a bit of borax, as the gold was fairly dirty.
It’s all a learning curve but I’m getting there. Thanks for the replies fellers.
Cheers Greg

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Re: Melting Gold

Post  goldhog22 on Sun Oct 09, 2011 5:52 pm

The cheepest way is to get some blacksmith coke and a small fan and set up a small forge that will melt anything.. Have used it my self and a small amount of charcoll helps keep it going first up.. can carry enough in a small bag to do a big melt...
Bob

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Re: Melting Gold

Post  koeh on Sun Oct 09, 2011 9:01 pm

Here is how I melt gold,

Put finds into a container with a drop of water and add a pinch of borax, mix well and wait to dry
fire up the oxy and slowly heat the crucible
then put a pinch of borax into the crucible and heat with oxy and chase the borax around the walls of the crucible
then pour mix of gold and borax into crucible and heat until molten
once melted all together, i watch as it slowly cools and when the time it right I hold the crucible with a set of pliers and gently pry the gold button out of the crucible with a knife/screwdriver and place into water, which will remove most of the flux of the gold button.
if you take too long to remove the gold button and it gets stuck, just reheat it and try again.

I found this to be the easiest way to do it than trying to pour the gold.



cheers

koeh

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Re: Melting Gold

Post  HOBO'S Gold on Sun Oct 09, 2011 9:17 pm

This might be helpful.

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Re: Melting Gold

Post  chopppacalamari on Sun Oct 09, 2011 10:17 pm

gee it looks beautiful doesn't it?
Mmmmmm!

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Re: Melting Gold

Post  koeh on Sun Oct 09, 2011 10:55 pm

there is one thing he didnt do was add some flux to the gold which will help it melt quicker, the way he is doing it he is using to much gas for his burner, the bottle would not last long.

cheers

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Re: Melting Gold

Post  phill on Tue Oct 11, 2011 9:21 pm

Hey guys, there are some terriffic suggestions coming out of this, I've been pretty busy lately and haven't had time to reply let alone watch the videos Johnny!
koeh, mate you sound right on the money.... thats pretty well exactly how I went about it barr from the premix with borax and dryout prior to the rest, albeit I used tweezers to grab them out of the cruicible.... little stuff
but will certainly do that step next time which will be very soon, you also sound like your better using the flux (borax) than I did so I'll improve next time I hope. Would also like to dolly up the next lot first, this lot I did I just heated the crucible, added borax (powder), made liquid, moved around to coat the crucible (this I did two or three times as advised by the sales gal) carefully added the dirty granules, and in other small lots, some small poreous nuggety bits up to about 3gms and with care kept the heat up and continued to add borax and melt it as it moved and congealed or amalgamated around in the pot.
The next melt I do I will viedo it and put it up for critique and ideas.
Keen to do some sizeable ones to Geof.....but I may need a bigger crucible..... Wink
Cheers, Phill


Last edited by phill on Tue Oct 11, 2011 9:26 pm; edited 1 time in total (Reason for editing : spelt do wrong.....)

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Re: Melting Gold

Post  Rob.B on Tue Oct 11, 2011 11:24 pm

Why do you guys melt down an individually looking, naturally formed nuggets to a non descript blob?

Serious & respectful question to which I'm sure there is a good reason.

I read somewhere that to test the difference between fools & good gold is to hit it with a hammer & if it flattens rather than shatters then its good gold. I was HORRIFIED!!!! Yes, its still gold, but it loses its beauty.

Rob


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Re: Melting Gold

Post  Guest on Tue Oct 11, 2011 11:28 pm

If you can't tell the difference between Mica or pyrite which ways nothing compared to Gold, then you have a lot of problems to overcome!
Not being nasty, just honest!

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Re: Melting Gold

Post  chopppacalamari on Tue Oct 11, 2011 11:37 pm

if you haven't seen it then I can under stand the question. That brings an old saying to mind. If you only think you have gold then you haven't. If you know you have gold then you have.

Dicko..

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Re: Melting Gold

Post  Guest on Tue Oct 11, 2011 11:42 pm

I look forward to the day when I need to concern myself with melting down my gold.

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Re: Melting Gold

Post  koeh on Tue Oct 11, 2011 11:42 pm

The only problem I has was when I melted 4oz's into a single button, the gold took that long to cool in the centre that you couldn't pry the button out of the crucible without deforming the button as the flux was cooling faster than the gold, so had to hit that crucible with a hammer to get it out, but 1,2,3 oz buttons are not a problem getting out.

The only reason that I had to wait for the flux gold mix to dry was that I had just sucked the gold out of a bluebowl, I would just pour off the excess water of my gold container (round takeaway dish) and add a tiny pinch of flux to the gold and mix it, as the borax helps with the drying of the gold and also coats the gold making it easier to melt.

cheers

koeh

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Re: Melting Gold

Post  Guest on Tue Oct 11, 2011 11:46 pm

4 OZ into a button, that's pretty sweet! I take it you sluice? Very Happy

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Re: Melting Gold

Post  koeh on Wed Oct 12, 2011 12:03 am

do a little panning in the wet season, have to do something to keep the gold fever at bay.

my profile pic is 1oz,2oz,3oz and 4oz buttons

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Re: Melting Gold

Post  Guest on Wed Oct 12, 2011 12:09 am

You'd swear that first bit is 4 X bigger than the last bit? Very Happy Very Happy Nice stuff Koeh.
Cheers Chris.

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Re: Melting Gold

Post  phill on Wed Oct 12, 2011 12:13 pm

Just to keep us up to speed with what constitutes what to melt down.

a few pics.....



Dirty sand like gold grains.





Small rough honeycombe pices.



Slightly larger dirty honeycombe pieces.



And, larger still, dirty honeycombe pieces....

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Re: Melting Gold

Post  Rob.B on Wed Oct 12, 2011 4:52 pm

I've never found gold, so I might have a problem knowing the difference between the real & fools?

I suppose we all have our special skills, I can look at charts & tell certian things in regard to a persons health, but that, like knowing the difference between good & crap gold is a skill. I hope to learn the skill with gold soon.

But that still doesnt answer why people mely gold from its natural unique form to a blob, or maybe I scanned past it?

Rob

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