[TheForge] Re: Flux, was rust & pickling-now magnetrons

Wed Aug 20 17:08:00 2003

I read the article.  I have seen it before.

Notes:

Taping over the holes in the cooking area can be detrimental to the
magnetron, in that the air that cools the magnetron is many times sent
to the cooking area as an additional heating load.  Blocking the holes
can block the magnetron cooling.

The crucible is coated with graphite, which is resistive, so this can
represent a load.  But not a load that could be considered quality<G>.

Power reflected back to the magnetron will cause overheating.  However,
if the standing waves are sufficient, arcing may occur.  The arcing will
travel back up the "waveguide" to the "transmitting element" of the
magnetron, and there arc arc across the insulator, thus killing the
magnetron.  Been there, done that, both on purpose and by accident.

It is possible to put your finger in a fan and turn it on.  You may well
survive it, and the fan also.  But it is never recommended<G>. However,
this is a good example of using something for a purpose for which it was
never intended.  Though good results may have been had by that
particular experimenter, using a different microwave oven and/or
changing the operating conditions can give disasterous results. At my
normal work location, we make a living out of making "parts" do things
which they were never intended to do.  We also build high power
transmitters, sometimes ones with magnetrons<G>.

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Bruce Freeman
Sent: Wednesday, August 20, 2003 4:33 PM
To: [email protected]
Subject: Re: [TheForge] Re: Flux, was rust & pickling

Chuck,
Very interesting, but he's GOT an absorber in the oven.  As he says,
without one, you can burn out your magnetron.  When the borax dries,
there's no more absorber, I think. Bruce

>>> [email protected] 08/19/03 09:12PM >>>
Hey Bruce,
If you think it would, check out this site:
http://home.c2i.net/metaphor/mvpage.html 
Chuck

----- Original Message ----- 
From: "Bruce Freeman" <[email protected]>
To: <[email protected]>
Sent: Tuesday, August 19, 2003 2:38 PM
Subject: Re: [TheForge] Re: Flux, was rust & pickling

> Chemicals can be dried with microwave energy.
> 
> I'd be concerned, however, that you might burn out  your magnetron 
> tube.
> 
> Bruce
> NJ
> 
> >>> [email protected] 08/19/03 03:16PM >>>
> Has anyone tried to dehydrate borax in a micro wave oven? Chuck
> ----- Original Message ----- 
> From: "Bruce Freeman" <[email protected]>
> To: <[email protected]>
> Sent: Tuesday, August 19, 2003 1:44 PM
> Subject: [TheForge] Re: Flux, was rust & pickling
> 
> 
> > This subject seems to come up repeatedly.  I don't know
specifically
> > about borax, but most inorganic chemicals start releasing their
water
> at
> > temperatures much below their melting points.  Working at about
350
> in a
> > standard oven would probably suffice.  Again, I haven't tried this
> with
> > borax, but I'd suggest trying it before going to higher
temperatures
> or
> > melting and regrinding it.
> > 
> > Many anhydrous chemicals, probably including borax, will absorb
> water
> > from the air.  However, the simple expedient of keeping it in a
> closed
> > container will protect it from air.  The short time it is open for
> use
> > will generally not result in a massive uptake of water.  I'd
suggest
> you
> > keep your anhydrous borax in a large jar, and pour it into a
smaller
> > jars for use.
> > 
> > Bruce
> > NJ
> > 
> > >>> [email protected] 08/19/03 12:45PM >>>
> > 
> > > So are you telling me that melting borax on an iron cookie will
> pick
> > > up some of the iron?
> > 
> > Following up to my own post...
> > 
> > How do you melt borax on a cookie tin?  The melting point is
around
> > 1500F, a red heat.
> > 
> > Checking in the handbook, borax loses 8 of its 10 bound water 
> > molecules at 140F and the rest at about 400F.  But it doesn't melt 
> > until waayyy hotter than that.
> > 
> > I never tried to dehydrate borax in the oven at, say, 450F.  I
> melted
> > some up last night over the forge in a cast iron ladle (kinda
> messy),
> > poured it into a cast iron bowl where it turned to black glass.
> Broke
> > it up into pea size, then ran it through an old manual meat
grinder
> > with the hamburger die modified to be more like a grain grinder.
> Nice
> > powdery stuff that should be good for flux.
> > 
> > Someone said that anhydrous borax will quickly re-absorb water
from
> > the air.  I think a maybe the advantage to bothering with melting
> and
> > grinding the borax is that in the glassy state it doesn't do that
> very
> > readily.
> > 
> > Just 'spearminting around...
> > 
> > - Mike
> > 
> > -- 
> > Michael Spencer                  Nova Scotia, Canada       .~. 
> >                                  
> >   /V\ 
> > [email protected]            
> >  /( )\
> > http://home.tallships.ca/mspencer/
> >  ^^-^^
> > 
> > --
> > 
> > 
> > 
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