From: REMOVE_THISdwilkins@means.net (Don Wilkins)
Newsgroups: rec.crafts.metalworking
Subject: Re: Microwave Foundry
Date: Tue, 12 May 1998 11:13:57 GMT

On Mon, 11 May 1998 08:35:50 -0500, Don Stauffer
<stauffer@htc.honeywell.com> wrote:

>DoN. Nichols wrote:
>>
>> In article <6j4aq7$f0m@pdrn.zippo.com>,  <David Anderson> wrote:
>> > - In article <35522567.6F31@nsc.com>, "Steven says...
>> >>
>> >>Now this looks interesting:
>> >>
>> >>http://binbro1.bitz.co.nz/people/dreid/mvpage.html
>> >>
>> >>Melting Metals in a Domestic Microwave
>> >>By: David Reid
>> >>
>> >>Certainly worth reading, although I'm not sure I will actually try it
>> >>myself.

I haven't read the book but it isn't as hard as you would think. It
turns out that silicon carbide couples with "kitchen" microwave oven
frequencies. My recollection is that silicon carbide couples even
better than the water molecule but I am not going to look it up. One
thing for sure is that you can get one hell of a lot hotter using
silicon carbide.

So there are some options. One is to use silicon carbide crucibles.
Reasonably inert but not cheap.

The other is to use granular silicon carbide as the inductor and some
other ceramic crucible as the container. I have seen conventional
microwave ovens used in this way to melt ceramic glazes on e.g. coffee
cups.

Granular silicon carbide is not that expensive. E.g. valve grinding
compound. Now if you melt a hole in your wife's microwave oven and the
hole continues into the basement because of poor design of the
insulating bricks and/or container please don't use my name when
justifying the experiment.

You can get a microwave oven from most pawn shops for under $50 and
avoid a multitude of domestic problems.

From: REMOVE_THISdwilkins@means.net (Don Wilkins)
Newsgroups: rec.crafts.metalworking
Subject: Re: melting metal in a home microwave oven
Date: Mon, 18 Jan 1999 14:19:02 GMT

On Sun, 17 Jan 1999 07:42:54 -0800, Grant Erwin
<meretrixNOSPAM@halcyon.com> wrote:

>This one opened my eyes. I found it quite fascinating. I believe
>it may be of general interest. This page asserts that a home
>microwave oven, with very minor mods (taping of vent holes ..)
>can be used to melt metals and presents a technique.
>
>Grant Erwin
>Seattle, Washington
>
>http://binbro1.bitz.co.nz/people/dreid/mvpage.html

I looked at this but did not read it in detail. It is a known
technique to get high temperatures in a conventional microwave oven. I
have not seen it used to melt metals before.

If they have some proprietary stuff to couple with the microwaves then
it is probably silicon carbide (valve grinding compound).

Silicon carbide cemented onto a suitable high temp brick can get you a
furnace that will go to red heat with no difficulty in a conventional
microwave oven. Those low density fire bricks work quite well. SiC
actually couples much better than water and won't boil or evaporate.

You do need to build a furnace where the SiC is a thin layer on the
inside of the brick used to build the furnace. The brick also of
course provides insulation so that the temperature inside of the
furnace is kept away from the sidewalls of the microwave oven.

This technique has been used to put glazes on coffee cups etc. for
quite a few years. Chemists also use it to run high temperature
reactions. We modified one so we could apply variable power.

If you want to try it visit your local pawn shop. They usually have
microwave ovens for under $50. If you goof and melt a hole through the
bottom or blow a tube it is a lot easier to sneak it out to the white
ware disposal area than to deal with an irate Frau in the kitchen.

From: REMOVE_THISdwilkins@means.net (Don Wilkins)
Newsgroups: rec.crafts.metalworking
Subject: Re: melting metal in a home microwave oven
Date: Tue, 19 Jan 1999 01:21:40 GMT

On Mon, 18 Jan 1999 14:19:02 GMT, REMOVE_THISdwilkins@means.net (Don
Wilkins) wrote:

>On Sun, 17 Jan 1999 07:42:54 -0800, Grant Erwin
><meretrixNOSPAM@halcyon.com> wrote:
>
>>This one opened my eyes. I found it quite fascinating. I believe
>>it may be of general interest. This page asserts that a home
>>microwave oven, with very minor mods (taping of vent holes ..)
>>can be used to melt metals and presents a technique.
>>
>>Grant Erwin
>>Seattle, Washington
>>
>>http://binbro1.bitz.co.nz/people/dreid/mvpage.html
>
>I looked at this but did not read it in detail. It is a known
>technique to get high temperatures in a conventional microwave oven. I
>have not seen it used to melt metals before.
>
>If they have some proprietary stuff to couple with the microwaves then
>it is probably silicon carbide (valve grinding compound).

Damn hate to follow up to my own post but I did go back and read the
whole thing when I had more time.

He is off to a good start and is using magnetite as the high
temperature suscepter. I am not sure if he should have given up on SiC
as quickly as he did.

Magnetite is Fe3O4 which also can be written as FeO.Fe2O3. It is a
spinel and there are a whole bunch of them which are known as ferrites
where the divalent iron (FeO) is substituted with other divalent
elements (e.g. NiO,MgO, etc.).

I ran a search and came up with over 24000 hits. I looked at the first
100 or so and came up with one which looked promising for those who
would like to pursue the topic.

Try

 http://www.staffs.ac.uk/engs/mgh/personal/pubs.html

and you should get a whole bunch of literature references concerning
the use of microwaves to heat ceramics. From there you will need a
good technical library or the patience to request reprints.