# GOLD SMELTING FLUX



## Dan72ccx

Looks very easy :mrgreen: 
http://www.youtube.com/watch?v=tB3oQeTG-Mc

http://www.legendsprospectingsupplies.com/index.php?act=viewProd&productId=137


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## Harold_V

This post is very interesting. I strongly advise those of you that do any smelting to investigate the concept. 
One note. In the video, the operator is shown stirring the material mid way in the operation. The harsh reality is that induction melting (that's what a microwave is, a small induction furnace, albeit high frequency) does not require stirring. The eddy currents developed provide almost violent stirring action. 

This setup could be the solution for those that have a desire to do their own assays, but do not have the capability to melt. It would not serve for cupelling, however. 

Harold


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## samuel-a

Harold_V said:


> albeit high frequency)



May serve well with PGM's black, won't you say so Harold?

I had a thought once of maybe using microwave for melting/smelting, but tossed that idea right out of my head, maybe it time to explore it again...
It seems too easy though... what are we not knowing?


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## Anonymous

Harold_V said:


> I strongly advise those of you that do any smelting to investigate the concept.


About 6 months ago,I built several different microwave kilns,using different products.I did not purchase anything from an online seller,I made them myself.They work well if all you are trying to do is melt something.In order to smelt something,it requires a powerful microwave.And Harold is correct,it does not work for cupelling.
I do not advise using this method for anything we do,that is why I never mentioned that I had built several different versions.If you have a high power microwave,it is a neat experiment,but it had better be a disposable microwave,or you had better plan on not doing it very long,or often.
As someone that has succesfully done this several times.....I'll stick to my torch and kilns.


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## Acid_Bath76

I looked into this less than a year ago, and dismissed the idea after reading some of the initial responses on this forum. Too bad I didn't research further. I have to say, this might be a viable option for someone looking for a compact, low profile, way to melt. I might give this a shot with one I can get from a thrift shop, or goodwill. Well see, right now I have enough on my plate. Interesting stuff though!


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## Anonymous

Yes...If all you needed was something to melt your refined gold,then it would work pretty good.I used various ceiling tiles and got good results,but you can try different materials and it will still work.


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## Geo

i talked to a guy that has done this and he used Cellpak insulation around the crucible. its made from newspaper impregnated with fire retardent chemicals. you cant burn this stuff with a torch.


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## Harold_V

samuel-a said:


> May serve well with PGM's black, won't you say so Harold?


It may have that capability, but you'd have to use a crucible that is capable of withstanding the temperatures involved. Those assay crucibles would most likely fail, leaving you in one hell of a mess. 

If you're not familiar with induction heating, as particles get smaller and smaller, higher and higher frequencies are required. Most any substance can be heated, assuming you provide the proper power and frequency. Given the fact that microwave oven operate at a high frequency, they just might be a natural for the PGM's black, assuming you could work out the issues with excessive heat. 

Key to success, at least in the one presented, is the extremely well insulated module that is used to house the crucible. Without that, you'd most certainly experience rapid failure of the oven. 

Harold


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## samuel-a

Good points to consider Harold. Thanks.

I'll sure build a kiln to protect the inner casing of the oven, that very easy thing to do.

Powders ware the first thing that came to mind when you mentioned high frequencies.

I actually have some white clay crucibles, i'm not sure of the composition, i think it's mixture of clay and Kaolinite... anyway, they hold up preety nicly, only start to liquify when Pt does with the oxy torch.
So i assume, since refacory materials do not run currents, the only heating of refactory will occur dou to projected heat of the metal. In any case, i don't mind if Pt / Ir button will get buried in the crucible, they come very cheap for me.

The only thing i can't wrap my head around is the dynamics during the melting, when the metal is molten, how does it still get inspired effectifly by the high frequencies?


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## Palladium

When heating items in a microwave you are actually passing a physical wave through a substance. Like shooting an arrow at a target. That’s why a microwave door has all them dots on it. It’s to stop radiation leakage. The cooking chamber itself is a Faraday cage which prevents the microwaves from escaping. The door usually has a window for viewing, but the window has a layer of conductive mesh some distance from the outer panel to maintain the shielding. Because the size of the perforations in the mesh is much less than the microwaves' wavelength, most of the microwave radiation cannot pass through the door, while visible light (with a much shorter wavelength) can.

When heating items with induction heating there is no physical wave. The waves are generated by induction, hence the name. It’s like waving a magnet in front of a iron bar and the electrons aligning to meet the pull of the magnetic field. Remember the trick in school where you run a magnet down a nail in one direction to make the nail a magnet? All the electrons orient themselves from the north and south or vice versa. Now do that 400,000 time a sec !!!! Both are done with magnetics so to speak, but one is bombarded with physical waves while the other occurs within the electromagnetic field itself.


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## catvet

The kiln looks like it would be relatively easily crafted from lightweight insulating firebricks, much like LaserSteve's minifirebrick furnace. The firebricks are quite readily available (refractory supplies in the phonebook) and fairly easy to work.


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## Acid_Bath76

if anybody is using this method, what are you using for the insulation housing within the microwave?


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## butcher

I have not tried melting metal powders in microwave. 
Acid_Bath76, please study microwaves well before trying anything, even though we think them safe being used in our kitchens, these are very dangerous if the safety's are compromised. 

I use to build and work on communication towers, the AM radio towers set on a porcelain ball, with porcelain insulators in the guy wires, the whole tower is the am antenna, we would have to jump from the ground to get onto the tower to climb it, they told us that if we touched the tower and the ground at the same time we would be fried like a bug in one of those electric bug zappers, once we were on the tower we would have to keep constantly moving or changing the hand we held onto the tower with, as if you held your hand in one spot too long it would burn you, and if you let go with that hand and did not have your self belted to tower you could fall 500 to 1000 feet depending on the tower and how high you were, my hands were burned several times, but never did let go with both hands, they told us it was burning us from the inside out, but we only felt it when it burned the nerve endings on our outer portion of our skin, was also supposed to make us sterile, but I had children so that did not happen, on TV towers there were two types of antenna’s bat wing and monopole, these are poles on top of towers, one you can climb Hot as long as you do not touch certain parts of it (instant death if you did), the monopole type you could not climb and had to keep several foot from antenna to avoid being fried.

since I am talking towers, years ago had a job to put up two antennas, and coax on a 500 ft tower, I was riding a winch line up, with the two antennas and coax up a 500 foot tower, got 60 foot up and the splice on winch line came apart, dropping me 60 foot to hard ground, me tied to a 150 pound weight I bounced about four feet after hitting the ground, had about 1000 feet of 3/8 winch line falling from the tower on top of me beating and cutting what was left of me, first thing I did was look over at the kid who was running the winch (also the college kid who spliced our winch into the tower line I was riding) he just sat starring at me, I kept hollering at him, finally after what seemed like a long time he realized I was hollering at him and run over to where I was and said what do I do, I told him we had a two way radio in the truck call somebody, (funny he went into shock but I did not, later when he visited me in the hospital ask asked him why he just sat there and froze, he said He knew I was dead, then he realized I was yelling at him) I powdered both femur bones in my legs broke some bones in my back. and was cutup pretty good, took four operations before I could walk on my own two feet without canes or crutch or wheel chair, even with rods in the bone centers, worked with four other men good friends who were not so lucky they fell to their death two over 250' and two over 500', as dangerous as that job was I miss it and would still like to do it again.

Well enough rambling on.


They use K-Wool fiber blanket insulation. they also do some modifications to the microwave (seems something to do with fan and stir plate, my memory foggy), also they use a suscepter or receptor of microwave energy (can not remember actual name) these are same thing the hot pocket card board coating is comprised of (I believe you could use other metal powders, or possibly graphite although I remember something about carbon not being that good to absorb microwave 2.4 GHZ.


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## NoIdea

Afternoon All - Microwave ovens can be alot of fun, read up on them first, as they have the potential to do great harm. 

Metal containers can be used in a microwave, i have dried forage in aluminium pie trays without any problems, it's not until the pie tray cracks then their is arcing. 

So the flux used, may have to contain small very high temp metals or oxides that will create arcing within the flux, the gold powder will also arc until molten, i could be wrong but the arcing could be the key to obtaining the required temperatures, and that's why he had to take it out and stirr. :?: 

In saying that, my experiance with microwaves are thus:
Steel wool = loads of sparks,fire, and UV radiation
Blown light bulb(filement detached completely) = tungsten filement melts the glass, preasure inside of bulb blows a small hole, outwards, looks real cool. Show friends and pretend you have NoIdea how it happened :mrgreen:


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## butcher

Also read up on microwave suscepter's, these seem to be the key, your powder particle size and amount per microwave wattage, the oxide powders or impurity metals may act as suscepter, but for pure gold powders you would probable need a susceptor in flux that would not render your gold impure, that seems to be a major hurdle, if graphite will not suffice???

it sounds like fun to expieriment with but the ole fashion torch, or gas furnace is just better in my eyes.


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## Geo

could be aluminum. it decomposes at the temperature that melts gold and has a reducing quality. you have to have aluminum to make good grade steel or the steel will oxidize making carbon. could be the same principle going on here, aluminum powder.


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## NoIdea

Hmmm, one needs to be careful with aluminium powder and metal oxides, OK if you want thermite, ahhh thermite :mrgreen: 

Deano


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## Geraldo

I think Butcher and NoIdea are on to something here.

I suspect that the person in the video is mis-using the word "flux" - rather the powder is a good microwave susceptor like silicon carbide. Microwaving heats up the silicon carbide, which is mixed with the gold powder and heats it up.

Not sure if that is a better approach than using a silicon carbide crucible, although SiC crucibles are probably expensive compared to alumina or fireclay or whatever he is using, while SiC powder is pretty cheap.

Now I need to find good insulating refractories and an old microwave in order to try that out...

Gerald


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## nickvc

While I'm sure that those writing and experimenting here on the forum are knowledgeable and know exactly what is going to happen I'm still sure this isn't one for the non expert to mess with.
I for one will not be trying any experiments with microwaves and will only even look at this seriously when one of the moderators gives it a full thumbs up as I'm 100% sure this could cause some serious injuries to someone not clued up on microwave energy, but I will continue to follow this thread with interest to see who sorts out the problems and creates the first safe forum model.


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## Acid_Bath76

I'm in the same boat on this one. My interest is peaked, but I'll be watching from the sidelines. If you want it straight from the "horse mouth", give them a call. When I first heard of this method, I did a little research, but microwave technology is a little over my head. For a lot of you guys though, you shouldn't have a problem picking their brain. I would be curious what you could walk away with after that conversation. Anyhow, you guys have a good one. I'm off to class. 

You may contact us at: 208.921.4561 or [email protected]


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## Anonymous

As I stated before,this method will work.I have performed it many times using various insulation materials,and fluxes.The success depends mostly on the microwave.A cheap wal-mart one will not get the job done.We have a commercial unit that came from a restaurant,and had no problems melting copper,and have had no problems with the mcrowave since my experiments, a year ago.


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## bswartzwelder

HELP! Does anybody know what formula would make a good gold smelting flux? I am planning on buying a kiln in the near future and the only formula for flux I have found is: 30 grams of ground sample + 30 grams soda (Na2CO3) + 30 grams lead oxide (PbO) + 2 grams flour + 10 grams silica sand. The problem with this is that any gold in the sample will end up as a button on the bottom of the crucible with the lead which came from the lead oxide. You then have to separate the lead by reheating it with the kiln door open slightly. This allow enough oxygen in to form lead oxide and leave any other metals in the sample behind.

I see that with the microwave method, once the melted mess is poured into a mold and allowed to cool, all that seems to be left is the gold and whatever else is in the glass mixture. I understand the glass mixture came from sand in the flux.


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## 4metals

There is a world of difference between a fusion which you are talking about and smelting. The lead from your fusion is removed by cupellation in a cupel placed in an assay kiln. 

What is your material that you are trying to smelt? I suggest you do some reading on the forum, all of the answers are here but it takes some commitment on your part to see it through.


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## bswartzwelder

I have been doing a lot of reading, but I seem to be more confused than ever. I wanted to see how much gold there is in various samples of black sand that I have accumulated. I suspect some of them migh be very rich in gold content. Also, if it is possible to separate the gold from the black sand by smelting, then that process just might be the answer to my questions. I am new to this and may not be using the right terms to properly phrase what I am trying to do. At some point, I want to refine what gold I have and pour it into ingots.


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## butcher

The problem I see with black sands is they are very high in Iron, magnetite and hematite, smelting, may just make a blob of Iron mixed with what little gold the had in them, that is if you were able to convert them to metals without them oxidizing in the melt making a slag of iron and tiny bits of gold locked up in them, Limestone (caco3), coal (coke), quartz (SiO2) are used to convert these iron oxides to metal in blast furnaces, not something easily done in your backyard.

just maybe with a flux very high in carbon (sodium carbonate) (or other carbon source like limestone) (coal and coke)to convert oxides of Iron and sand, borax to help make sand or quartz a glass slag for base metals to gather, something like fluorspar to help dissolve and make liquid, and a metal collector like lead, you may get a small bead, like they would in an assay, but by the time you wasted all of that time experimenting failing and wasting of furnace gas and dissolving good crucibles to find a mix that may yield tiny minimum amounts of gold, you would probably still find yourself in the hole as far as cost.

My thinking is if you can not classify it and pan it out is most likely not worth fooling with unless you had many tons of this, then sell it to china.

Sluicing, blue bowl or shaker tables if you have more than you care to pan.

Trouble with leaching is getting rid of all that iron; it wastes all your money on acids and oxidizers trying to get the iron out.

This is just my uneducated answer to your problem


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## 4metals

I agree with Butcher, the iron is your problem here. Have you tried an amalgamation test? That will give you an idea of how much gold can be recovered from the ore by amalgamation. If it is substantial then you know you have something. 

The amalgamation test is not considered as a method of assay capable of telling you the total gold content of the ore, only the gold recoverable by amalgamation.

If you want to fire assay the material you need to make up a flux like this;

sample size 1/2 assay ton (an assay ton is 29.166 grams)
sodium carbonate 20 g
borax glass 15 g
litharge 35 g
Flour 4 g
Flourospar 5 g
silica 20 grams

If the ore contains silica you can reduce the silica in the charge. 

This will produce a bead containing all of the precious metals after cupellation in a bone ash cupel.


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## solar_plasma

In this thread you discussed about microwave...

Here are links of a german institute for further education on the field of chemistry, that show how to find the hot spots in a normal microwave and how to build a diy crucible that uses a layer of graphite spray to gain temperatures above 1000 degrees celsius. They form brass alloy with that project:

finding hot spot with thermo fax paper: http://www.chf.de/eduthek/mikrowelle-experiment07.html
crucible with graphite layer: http://www.chf.de/eduthek/mikrowelle-experiment09.html
brass alloy: http://www.chf.de/eduthek/mikrowelle-experiment10.html

...kinda ingenious!

When I sooner or later have obtained experiences with it and if it will be usable for our subjects of interest, I will write a description in english.


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## butcher

The graphite is the microwave susceptor material, there are several materials that can act as microwave susceptor material, that can absorb heat from the microwave energy to help give the heat needed to melt the metals.
http://www.google.com/#hl=en&sclient=psy-ab&q=microwave+susceptor+materials&oq=microvave+susc&gs_l=hp.1.1.0i13l4.2168.9539.0.14952.14.13.0.1.1.0.2372.10476.2-2j2j1j2j3j1j1j1.13.0...0.0...1c.1.7.psy-ab.ZqTFosdpU0A&pbx=1&bav=on.2,or.r_qf.&bvm=bv.44442042,d.cGE&fp=aa7899e64e1d28d6&biw=1024&bih=594


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## vyper

Would a process like this be feasible for cons derived from incinerated flatpacks, IC's etc. Not worried about the microwave portion of it just if there's a flux one could use to remove most of the junk from the cons? Then refining from there once you had a good amount of conical buttons to do so.


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## bswartzwelder

A lot of the iron in the black sands can be removed with an ingenious new device called a magnet. Drop a magnet into black sands and the hematite wil be attracted to it leaving the non magnetic portion of the black sand behind. WOW technology never ceases to amaze me. One caveat, I don't know if the gold is alloyed with the hematite or not. If it is, throw the magnet away. Also, from what I've read, a ton of black sand only yields an ounce or maybe two of gold. Usually gold is found with black sand, but not all black sand contains gold.


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## vyper

Take it that's a no?


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