microwave gold smelter

[haveagojoe]

The water in the potato will steal a significant amount of heat.
Drop the potato.

Will it? Or will it help to insulate? I'm hoping to hear from someone who has actually tried it, since the user who claimed it works is no longer active.
I will try it with my next batch of powder but it probably won't be soon.

 

[Shark]

A few more questions for those using microwaves to melt with.

Microwaves come in different output ranges. Do you really need the industrial size microwave or will the common cheap ones work?

How long does it take to melt an ounce of gold in one? Will a larger 220 sized microwave be quicker?

Electricity isn't cheap these days, so how much would the average cost of using a microwave be versus a common propane torch?

Melting less than an ounce it seems hard to beat the basic tools. I have seen 2 grams melted in a dish on ceramic wool using a cigar lighter. It worked, but I wouldn't call it efficient. If I already had everything on hand, I would try it. Even used microwaves cost a bit and the fire brick, if you don't have cheap access, is costly. A propane torch can be had cheap, and a layer or two of sheet rock works really well for insulation.

 

[haveagojoe]

Microwaves come in different output ranges. Do you really need the industrial size microwave or will the common cheap ones work?

Owltech says he's tried it here, using only a 700w microwave. From what I've gleaned, it needs to be the traditional non-invertor type, the more modern ones with an invertor won't work

How long does it take to melt an ounce of gold in one? Will a larger 220 sized microwave be quicker?

I think a whole ounce would be too much to ask of a microwave. I may be wrong. However in the videos he melts 6g in 8 minutes with no fuss, Owltech claims 10g, which seems very handy for anyone working at that small scale.

the fire brick, if you don't have cheap access, is costly.

Hence my interest in potatoes!

A propane torch can be had cheap, and a layer or two of sheet rock works really well for insulation.

Personally I've found propane to be insufficient unless used with compressed air at the inlet. MAPP gas works ok but it's expensive and still takes quite a long time, a whole bottle of gas can be gone on a single button.

 

[Yggdrasil]

Will it? Or will it help to insulate? I'm hoping to hear from someone who has actually tried it, since the user who claimed it works is no longer active.
I will try it with my next batch of powder but it probably won't be soon.

There are several videos out there.
Even two at instructables, and you can even buy conversion kits.
So it is doable.

As regarding to the water in the potato.
Water has a very high specific heat which means it needs high amount of energy to become hotter.
Additionally the phase change from liquid to vapour also is a hog of heat.
The only good thing is that potatos are cheap.

 

[4metals]

I had never heard of using a potato as a crucible before but in Ecuador in the late 1980's we were cleaning up black sands and processing them into mercury amalgam. The lumpy amalgam was squeezed through a chamois cloth to leave behind a doré of metal contaminated with a little mercury. The locals used a potato in which the dirty gold was placed in a hollowed out cavity and wrapped in heavy tin foil and thrown into a camp fire. The gold never melted because it never got hot enough in a campfire but the mercury volatilized off and was captured in the potato leaving the doré mercury free. I have heard this is a common trick with placer miners around the world.

I, however was a rather well equipped gr***o nerd from America so I had, and used, a retort to distill off and collect the mercury.

This is likely a case of the same vegetable but a different application.

 

[haveagojoe]

The only good thing is that potatos are cheap.

Well also I guess you'd have pretty much zero losses if it had the lid on in the microwave. And there's something to be said for the convenience.

I'm not sure about the water. I think it makes a difference that the water is trapped within the potato's cells, and the potato has its skin on. If you imagine cutting open a baked potato, a load of steam comes out which couldn't get out during cooking.

Here's a video of a guy melting gold in a potato crucible while holding it in his bare hand! Obviously pretty dangerous and not recommended but it's a testament to the insulative qualities of the potato. Holding a conventional crucible like that would be impossible, I daresay even in rockwool wadding.

In this video, the guy notes that unlike a crucible, the potato doesn't retain any gold around the edges. He picks up the potato containing a significant amount of molten gold barehanded.

Still hoping there's someone here who's tried the microwave potato, or is willing to have a go in the name of science...

Edit to add: of course also the potato can be carved into any mould shape which might be desired...

 

[Yggdrasil]

Well also I guess you'd have pretty much zero losses if it had the lid on in the microwave. And there's something to be said for the convenience.

I'm not sure about the water. I think it makes a difference that the water is trapped within the potato's cells, and the potato has its skin on. If you imagine cutting open a baked potato, a load of steam comes out which couldn't get out during cooking.

Here's a video of a guy melting gold in a potato crucible while holding it in his bare hand! Obviously pretty dangerous and not recommended but it's a testament to the insulative qualities of the potato. Holding a conventional crucible like that would be impossible, I daresay even in rockwool wadding.

In this video, the guy notes that unlike a crucible, the potato doesn't retain any gold around the edges. He picks up the potato containing a significant amount of molten gold barehanded.

Still hoping there's someone here who's tried the microwave potato, or is willing to have a go in the name of science...

Edit to add: of course also the potato can be carved into any mould shape which might be desired...

Search specific heat of water.
But then again you seem to have made up your mind.
There is a reason for all the kits being made of Silicone Carbide and not a water based mechanism.
The good thing of the microwaves is that they heat the water and the metal directly and while water is a relatively bad conductor of heat the metal receives the brunt of the energy.
And if it is melted sufficiently fast the metal will melt before the potato is cooked.
There is one application where a potato makes sense and that is if you are melting amalgam.
As the Mercury will be trapped by the potato.

 

[haveagojoe]

Search specific heat of water.
But then again you seem to have made up your mind.
There is a reason for all the kits being made of Silicone Carbide and not a water based mechanism.
The good thing of the microwaves is that they heat the water and the metal directly and while water is a relatively bad conductor of heat the metal receives the brunt of the energy.
And if it is melted sufficiently fast the metal will melt before the potato is cooked.
There is one application where a potato makes sense and that is if you are melting amalgam.
As the Mercury will be trapped by the potato.

Yes but it's not just a cup of water, it's tiny particles trapped inside cells. Convection is restricted, like bubblewrap.
Check out the videos I posted above of people torch-melting gold in potatoes. There are quite a few others, silver too. Of course it's not going to be as good as using a purpose made crucible, but if it works with a torch I can't see why it wouldn't work in a microwave. I haven't made up my mind though until I try it or at least hear from someone who has.

 

[4metals]

I learned something today, for a very small amount of gold a potato makes one ugly bead and the small pieces may get lost in the spud. For a larger melt, the surface tension of the molten metal will at least hold it together. As far as making a bead with any chance of a buyer being interested, I would use a proper melting dish.

But the potentially life saving knowledge gained from this discussion is that if I ever find myself in the path of a pyroclastic flow, I'll find a pile of potatoes to hide under.

 

[Yggdrasil]

Yes but it's not just a cup of water, it's tiny particles trapped inside cells.
Check out the videos I posted above of people torch-melting gold in potatoes. There are quite a few others, silver too. Of course it's not going to be as good as using a purpose made crucible, but if it works with a torch I can't see why it wouldn't work in a microwave. I haven't made up my mind though until I try it or at least hear from someone who has.

Of course it works, but as I say it will "steal" a significant amount of energy.
It do not matter if it is liquid or in a fruit, water is water.
In this case the energy is probably in surplus (depending on the micro) so it won't matter too much.

 

[haveagojoe]

It do not matter if it is liquid or in a fruit, water is water.

It does, otherwise it would take the same amount of time to boil the water inside a potato as it does to boil an equivalent cup of water. When cooking a potato in a conventional oven ie from the outside, the middle takes a lot longer to cook. The cellular structure restricts convection. That's why the guy in the video is able to touch the outside of the potato while it has molten gold inside it, whereas the temperature at the outside edge of a cup of hot water is the same as in the center.

 

[goldshark]

The only experience I have had with a microwave, is trying to roast a small batch of sulphide/ Gold concentrates in a plastic gold pan. Needles to say, this was a learning experience. The concentrates become very hot quickly, melting a good divot in the plastic. I removed promptly, and never tried it again. I would think that a melting dish with Kaowool underneath, would work effectively for small amounts of metals. I would preheat the melt dish, so it doesn't crack when heated too quickly by the metal.

 

[haveagojoe]

a melting dish with Kaowool underneath

The kits sold for doing it use an insulative box with a lid to retain enough heat. I have seen a DIY version made from ceramic wool bound with kapton tape. But I think a potato could work almost as well.

 

[goldshark]

The kits sold for doing it use an insulative box with a lid to retain enough heat. I have seen a DIY version made from ceramic wool bound with kapton tape. But I think a potato could work almost as well.

Looks like you are going to be our go to guy on this. Please let us know how it works out. Did you tell your mom what you are about to do?

 

[Yggdrasil]

The kits sold for doing it use an insulative box with a lid to retain enough heat. I have seen a DIY version made from ceramic wool bound with kapton tape. But I think a potato could work almost as well.

Did you check out the instructables?
It even explained how to make your own Silicone Carbide crucible.

 

[4metals]

This is one place to buy one. Gold miners tools

Coincidentally on the bottom of the microwave add they have a mini propane gas burner furnace too. Buy one of each to save on freight!

 

[haveagojoe]

Looks like you are going to be our go to guy on this. Please let us know how it works out. Did you tell your mom what you are about to do?

I don't have powder at the moment but for sure I will make a post when I try it. I was hoping that someone else had tried it other than SSBog. I suggest @Owltech is the go-to guy for microwaves, since he has actually done it and made videos about it, although sadly they are now set to private.

 

[haveagojoe]

How long does it take to melt an ounce of gold in one? Will a larger 220 sized microwave be quicker?

Here's some guys smelting in larger pours, no idea on how long it takes to melt but impressive to see it's possible

 

[4metals]

some guys doing larger pours,

What part of large pours did I miss? Those are assay sized pours!

And the entire process could have been done with the gas furnace.

Sorry not a microwave fan yet!!

 

[haveagojoe]

What part of large pours did I miss?

Larger, as in more than a few grams. Shark was asking about 1oz which those appear to be (108g/3 pours- although he says they started with 1oz of ore each time, which doesn't add up).

As a hobbyist my interest is in the <1oz range, perhaps one day I'll get an ounce together. Clearly this approach would not scale for the larger operators such as your goodself, but as is often said here it's always a case of matching the process appropriately with the materials and tools.
And it makes for an interesting discussion at any rate.