microwave gold smelter

[Owltech]

His secret is the ferrite. The melting dish sits on a bed of broken ferrite (like the one found in old CRT TVs or cable EMF shields), that absorbs the microwave energy. The generated heat is transferred to the crucible and then to the metal to be melted. I think the ferrite serves the same purpose as the graphite crucible in the induction furnace.

 

[frank-20011]

hello,

"His secret is the ferrite. The melting dish sits on a bed of broken ferrite"

i this video you can see ferrite:

https://www.youtube.com/watch?v=ogZvX7w9ZDo

but in this one (the same you have shown) there isn't any ferrite...so what's the explenation in this case?:

https://www.youtube.com/watch?v=1fc-YoiSKfY


greetings!

 

[Owltech]

in the one I've posted he uses graphite, but later on he improved his setup by replacing it with ferrite. He has many videos on the subject experimenting with different materials.

 

[frank-20011]

hello,

i will no doubt in your opinion but i can not see anything black.

maybe it is IN the refractory cement the whole "construct" where the melting dish is sitting in is made of?

Yes, in other videos you see a bed made of ferrite but in those you have posted i can see only the white refractory cement!

Anywhere it MUST be but i can' t see it!

best regards!

 

[Owltech]

it is not a refractory cement, it is an alumina silicate board. I tried to melt silver without the improvements (graphite or ferrite) and it worked but it is slow.

In this video the guy uses only kaowool board without ferrite or graphite
https://www.youtube.com/watch?v=1xDQJYfQySk

 

[JoeyJoystick]

My 2 pennies worth...

I see a comparison between induction and microwave. Yes there is some common ground here but also some major differences.

An induction oven heats by Electrical Induction whereas a microwave oven heats by using microwaves. That is a significant difference.

The size of the load determines the frequency in an induction oven, and the frequency has a major impact on the penetration depth of the electrical induction into the material you want to heat. I must admit that I am not sure how the product influences the frequency though.

When using a microwave on the other hand, you are directly exciting the atoms making them move faster and hence getting hotter.

Both systems have trouble penetrating deeply. With an induction oven this is solved by varying the frequency. This can be done automatically. Not 100% sure, but I am guessing that the system tries to find its resonance frequency. This is different for every product and also the amount could have an impact on this. With a microwave you do not have the luxury of tuning during operation as far as I know.

The frequency for induction is in the range of several kHz to 10's maybe even a few 100kHz. With microwave ovens this is more in the order of GHz. 2.4GHz is the commonly used frequency in home microwave ovens. It is not true that this is the frequency that works best on water. There is plenty of microwave ovens that work on different frequencies. 900MHz is a common frequency for magnetrons used in microwave ovens as well.

Induction furnaces are cooled by water running through the coil. But they are also able to produce extremely high power. 10kWh to many MWh

Microwaves can be produced in the range of MWh but I do not know of ovens that do so. These high power ratings are often used in the military. Normally, and what is being talked about in this thread, is obviously the home use microwave ovens for cooking. These are always air cooled with a simple fan behind them. High power units are water cooled, but are very expensive.

And talking about price, the interesting thing about using a microwave oven for gold is the price. A 900W magnetron (the microwave transmitter) costs about $15.00 and the control electronics is between $10 and $15. Or you can take them from an old microwave oven for free.

Regarding safety: Yes we should be careful using microwaves. However, when contained inside a metal box, it is safe as far as radiation goes. Microwaves are not the penetrating kind of waves as we know from x-rays or gamma rays.

Some testing would be great and I am wondering if more power would actually allow to melt more gold as well or simply melt it quicker. It would be easy to set-up an array of 4 of these transmitters on 1 side of the containment box. I have not heard of this being done before, so this should be done carefully the first time.

The good thing is that, much like the induction furnace, you are heating the product and not the crucible containing it. The heated product will obviously heat the crucible, but this way you loose way less energy than when you are heating the crucible and letting the crucible heat up the product which is what is done in a classical furnace.

I am seriously considering this as an option for a lab furnace if (a big if for now. First need to learn an awful lot more...) I am to pursue gold refining. For large amounts as mentioned by others, I would probably use an induction furnace or a gas fired furnace. What I like about electrical furnaces is the cleanliness. It is a lot less unhealthy than a fired furnace. And since both induction and microwave are contained, it will also allow you to fairly easily heat under Nitrogen or Argon.

I personally think that microwaves should be taken seriously.


Joey.

 

[rickzeien]

I think the industry is heading towards Solid State Microwaves. Could prove useful in melting furnaces. Zones. Inert atmosphere. Vacuum. Pressure. The potential is enormous.

https://www.macom.com/blog/the-evolution-of-the-microwave-f

Sent from my SM-G950U using Tapatalk

 

[anachronism]

It's really easy if you know how.

 

[g_axelsson]

I thought the trick of melting metal in a microwave oven was to use a silicon carbide crucible as that absorbs the microwave energy. Pure metal is a good reflector, it doesn't heat up from micro wave frequencies.

The trick of melting stuff is a balance of energy deposited and energy lost. If you can minimize the losses then you can create bigger melts or melt stuff faster. The time it takes to melt something is depending on how much build up of heat you can get combined with the weight of the charge. For example, a small charge will heat up faster than a large charge, but if it is done in the same crucible with the same insulation then the ultimate temperature will be the same in the end.

It's just simple physics!

By the way, induction ovens do work best at resonance and the larger the charge the lower the frequency.

Göran

 

[SGBog]

Microwaved smelting in potato for 10min no sparks because I put the top back on the potato. No metal exposed no sparks.

 

[anachronism]

Microwaved smelting in potato for 10min no sparks because I put the top back on the potato. No metal exposed no sparks.

Yeah I agree that would work. Same as putting things in cardboard, or using the methods mentioned above.

 

[haveagojoe]

Microwaved smelting in potato for 10min no sparks because I put the top back on the potato. No metal exposed no sparks.

Wanted to revive this thread, this suggestion in particular I think is genius and would be very helpful for the amateur. I've heard of torch melting in a potato, and melting in a microwave, but putting the two together is a great idea. Anyone else tried it?

 

[haveagojoe]

Despite the initial words of warning and skepticism in this thread, there's a guy apparently using a microwave as part of his regular setup here and here. Not with a potato though. And without gloves

 

[4metals]

For a beginner, especially one with a wife who uses her microwave daily for cooking, there are better and simpler options. Like this.

 

[haveagojoe]

For a beginner, especially one with a wife who uses her microwave daily for cooking, there are better and simpler options. Like this.

Obviously a dedicated microwave is required, even without a wife, but I'd say it can't get much simpler than a potato Cheaper than gas too...

 

[4metals]

One of the issues with a microwave melter is capacity. Anyone venturing into refining with any degree of seriousness should consider growth and versatility and even feedstock. For this reason I question the logic of a microwave setup. If you plan to refine jewelry via inquartation size matters. True that also rules out the small brick furnace I linked above as well but the brick setup is an inexpensive starting furnace.

As an example watch some video's of sreetips in the video section and notice the majority of his melting is via a torch. That shows the versatility of a torch in refining. If I was starting out as a hobby refiner with interest towards earning income from it, my melt capacity pecking order would be
1. the mini brick furnace
2. a good torch (as in oxygen/compressed air and propane.)
3. A gas crucible furnace with at least a #6 crucible
capacity.
The microwave wouldn't make the cut!

 

[4metals]

From a "hobby" refiner up to a "make some cash" refiner the member that comes to mind for me is @Shark. I would like to hear his progression through the melting furnace options. He has done everything from foils through smelting as well as karat and silver so I would value his experience on this issue.

 

[Shark]

I started with a oxy/propane cutting torch, light duty. It is still my main go to for PM melting in a dish. I have an oxy/acetylene heavy duty as well but seldom use it. I have a large medium duty propane torch used to heat molds with and incinerate small batches of chips with. And a large one that runs propane and can put out 65,000 btu's. In cooler weather it tends to freeze the tanks up if not heated.

My first melting furnace was a gift. I don't recall the size crucible it uses but it only holds around 2 pounds of copper. I still lean on it pretty hard although it is coming apart after 7 plus years using it. It can be seen in the thread about smelting copper and the copper cell thread in the Library section. That little furnace has melted around 150 pounds of gold bearing copper for my small copper cells. I have another one that was made from a freon tank as well and the crucible holds around 20 pounds of copper or brass. Mainly used on chips per @kurtak's information on incinerating and smelting chips.

I have used and still do occasionally the small one brick furnace 4metals mentioned. They work great when shaped right. If using a straight propane or Mapp torch they help greatly. If your lucky enough to have shops nearby that work on industrial furnaces you can often find lightly used soft furnace bricks cheap. I bought 60 about 8 years ago for $30. Still have enough to do one more larger furnace with. There used to be several iron foundries in our area.

My first pound of gold was melted in small dishes an ounce or so at a time. I do have one that can do up to 6 ounces but never used it. I don't have a mold so I let them cool in the dish and pick them out before they freeze to the dish.

Although I find it interesting, I have never thought I needed a microwave other than to heat my coffee once it gets cold. Maybe a hot snack once in a while.

That's a lot of yap from me, but hope it helps someone down the road.

 

[haveagojoe]

@Shark Thanks, that's useful experience to hear, but in this thread I am interested to hear from anyone who has used a microwave for melting gold, since from the videos I linked it clearly works on the kind of scale hobbyists commonly work with. There isn't much on Youtube about using microwaves for gold specifically, and it's something which hasn't recieved a lot of attention so I thought it worthy of renewed discussion.

@4metals If it can melt 6g as it seems from the videos, I'd say it could make the cut for many, not for inquarting karat scrap, indeed, but for escrappers making small buttons it could be ideal. It takes a lot less gas to melt a handful of buttons together at the end than to use gas throughout.

Here the same Youtuber My Adventure reviews the microwave melt kit, and mentions the cost and efficiency advantages over gas, saying that he no longer uses a torch. From his other videos he appears to be quite knowledgable about the whole process so I am tentatively persuaded.

However it was the suggestion of using a potato that really caught my attention, I'm interested to hear if anyone has tried, or is willing to experiment, using a potato as the combined crucible and insulator in a microwave. User @SGBog who suggested above it is no longer active and made no other posts. The potato crucible is an old trick but I can see it working well in a microwave since it provides a good layer of insulation; potatoes hold heat quite well- as we know they take a while to cool enough to eat after cooking.

 

[Yggdrasil]

@Shark Thanks, that's useful experience to hear, but in this thread I am interested to hear from anyone who has used a microwave for melting gold, since from the videos I linked it clearly works on the kind of scale hobbyists commonly work with. There isn't much on Youtube about using microwaves for gold specifically, and it's something which hasn't recieved a lot of attention so I thought it worthy of renewed discussion.

@4metals If it can melt 6g as it seems from the videos, I'd say it could make the cut for many, not for inquarting karat scrap, indeed, but for escrappers making small buttons it could be ideal. It takes a lot less gas to melt a handful of buttons together at the end than to use gas throughout.

Here the same Youtuber My Adventure reviews the microwave melt kit, and mentions the cost and efficiency advantages over gas, saying that he no longer uses a torch. From his other videos he appears to be quite knowledgable about the whole process so I am tentatively persuaded.

However it was the suggestion of using a potato that really caught my attention, I'm interested to hear if anyone has tried it, or is willing to experiment using a potato as the combined crucible and insulator in a microwave. User @SGBog who suggested above it is no longer active and made no other posts. The potato crucible is an old trick but I can see it working well in a microwave since it provides a good layer of insulation; potatoes hold heat quite well- as we know they take a while to cool enough to eat after cooking.

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