Mississippi Mud Caps: Was, Barium Titanate Caps.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <uncadoc-at-juno-dot-com>

Hi Terry, Gary, Ed, Dr. Cadd, Jim, Dunckx, Georg, All.  Thanks for
bearing with me!  The original concept was to use a force sieve with a
hydraulic jack to force only the purest part of the clay, which had first
been churned and dampened in the 1/2hp gearmotor 30rpm 'mud pot', so that
it was a slurry. We mixed red and white clay together in equal
proportions. The slurry was then forced through another series of screens
of diminishing size to result in a fairly pure compound of "Mississippi
Mud".  The resulting slurry was set aside to solidify or dehydrate
somewhat to rid excess moisture.  The resulting somewhat pure clay was
then mixed again(churned) with a small portion of auto body resin to act
as a plasticizer.  This gave us a kneadable smooth mixture without air
bubbles to roll out into a slab of roughly 1/2" thickness.  The clay
slabs were cut into 6"x6" squares and a film of sheet copper shim was
placed upon the wetted sides of the center slab, top and bottom. This was
then pressed and then a upper and lower sheet of 1/2" plasticized clay
were applied to the top and bottom of the copper shim stock.  This was
hard pressed once again.  Now we have a sandwich of
clay-copper-clay-copper-clay about 1and 1/2" thick x6" square.  We then
placed  the clay sandwich into the microwave and nuked it on max (1,000
watts) for 60 seconds.  This solidify's the mass somewhat and draws off
some of the water.  The heated sandwich is then placed between a welded
up set of steel platen plates with sides and treated with a mold release
agent and then pressed with a hydraulic jack.  The sandwich is then
removed and placed into the microwave again at max. for another 60
seconds, removed and pressed again into its "waffled" form.  It now is
removed and a 3/8"hollow diamond core bit is used with hand power very
carefully to remove a plug of clay from the top and bottom layers of clay
to the copper sheet.  The exposed portion of sheet is cleaned,
burnished,tinned and soldered to a 16ga. stranded copper/silvered wire to
provide terminal leads.  We then nuked the wired slab one more time for
two minutes on max. and removed the slab and placed it in the electric
kiln at 1200F for 24 hours, at which point the kiln was de-energized and
the slab was left within to slowly cure for 48 hours.  The cured clay
slug was then removed and we noted a number of sticky blackened globules
around the perimeter of the slab, perhaps some off resin from the body
putty plasticizer?  Not sure at this point but some scrubbing with a
stainless steel brillo pad and white vinegar cleaned it up nicely.  The
clay capacitor was then tested for leakage on the vom, looked ok, and we
put it on the old 'magic eye' cap meter and it read out as .005uf.  We
then filled up the top wire lead hole with 5 minute epoxy, let set and
then flipped it over and filled the other wire lead hole. We then filled
the bottom of a roughly 7" square tupperware type plastic container with
slow set epoxy at a depth of 1/2" and placed the clay capacitor into the
mix, only after coating the bottom of the capacitor completely with epoxy
and making sure the wire lead was extended, so that it would be
retreivable at the bottom of the cured epoxy.   We then filled the rest
of the container with epoxy to cover the top of the cap. with wire lead
extended above top and then filled with the epoxy to a depth of roughly
1/4".  We let this set for two days.  We then cut off the old
'tupperware' mold and tested the cap again with our primitive equipment.
It looked good!   It is still air curing tonight, but we wanted to test
it under fire, so we hooked it up to our old OBIT coil with salt water
caps, and viola, it worked!  We only needed two bottle caps in
conjunction with our clay contraption to fire the coil with good results!
  We ran it at ten second clips with no sign of overheating.  We now need
to make more to try with the 15kv modified neons to see if they will
withstand that voltage and higher current,  and for how long a period of
time.  Our greatest fear is that the clay will crack internally within
the epoxy shell at higher volts and amps, but we think that if we can
stack them as a long multicelled epoxy encapsulated capacitor, then they
may even survive a pole pig ordeal.    Al.

On Sun, 22 Apr 2001 20:06:04 -0600 "Tesla list" <tesla-at-pupman-dot-com>
writes:
> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
> 
> Hi Gary and Al,
> 
> Ok, now that we have all three had our say about my killing the 
> barium
> safety thread (which "I" am solely responsible for), let's get down 
> to the
> cool stuff.
> 
> Al, how in the world are you planning on making these caps?  I 
> assume you
> need fairly high quality clay (ceramic) and you need to fire it 
> somehow
> with interleaved plates inside.  I am very familiar with high power 
> RF caps
> like ATC makes.  The ceramic, plates, tolerances and such are pretty 
> high
> quality and tolerance.  But they are trying to make the caps small 
> too.  So
> making them simply in larger dimensions should ease that problem
> considerably.  I can see aluminum foil with clay layers in between.  
> Air
> bubbles in the clay could be a big problem.  I wonder if something 
> like
> plaster of Paris would be better.  However, the dielectric is still 
> going
> to have to be low loss or the heat will kill it.  Loss my be a 
> problem with
> red clay that I think is red due to iron oxides...  Not really 
> sure...
> Impurities could be a big problem too.
> 
> Maybe study the early days of ceramic cap making for tips.  They had 
> pretty
> "basic" tools back then so maybe their techniques would not be hard 
> to
> reproduce.  You have today's technology too to steer you in the 
> right
> direction and around problems the early guys had.  Since you may 
> work with
> far larger dimensions, perhaps much lower grade ceramics can be 
> found at
> much lower cost...
> 
> Cheers,
> 
> 	Terry
> 
> 
> At 07:59 PM 4/22/2001 -0500, you wrote:
> >Hi Al:
> >
> >Please don't cast me as a sinister conspitator.  My goal was not to
> >"outlaw" or stiffle discussion on new or different means of making
> >capacitors, but simply to point out that the NUMEROUS posts on the 
> topic
> >snip... 
> 
> 

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