Re: X-ray film capacitors

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Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Chris, Fred (again!) All!

>Remember, some films (I don't know if X-ray works this wa or not)
contain
>Silver Halide as the photoreactive chemical. Last time I checked
silver was
>a rather good conductor. This could have catastrophic results in a
>capacitor.  But I don't know enough of the chemistry of X-ray
photography to
>really say. Anyone out there know?


I'd assumed that the film referred to was "spent" i.e. it had been
through processing etc and was basically the bare backing.  Evidently
not.  My mistake.

Sodium thiosulphate, aka "hypo", aka "fixer", will dissolve out all
silver salts from the film if the film hasn't been developed.  (If it
has been developed, the hypo only removes the silver halide which
wasn't exposed to light; it is the function of the developer to reduce
chemically the silver halide which has been sensitised by exposure to
light to metallic silver thus forming the image.  If the film has been
exposed but not developed, the hypo will strip the lot.)  This stuff
is cheap, non-toxic and easy to use.  Any photographic supplier will
stock it.  Dissolve say 8oz hypo per pint of water.  Agitate film in
the solution for say twenty minutes and wash it in clean water
afterwards for a similar time.  Considering that you want to use the
film for EHT, you might want to give it several washes to be sure all
the muck is rinsed out.  Obviously, dry well before use.  If you are
"fixing" vast quantities of film, recovery of the silver from the hypo
solution may be worthwhile (thinking of fund-raising here ;-).  I know
there are professional photographers on the list and hope they will
comment further.

Dunckx
Geek#1113 (G-1)