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Re: [Rollei] Film washing technique

- ----- Original Message ----- 
From: "David Seifert" <dseifert  >
To: <rollei  
Sent: Friday, May 02, 2003 8:28 PM
Subject: Re: [Rollei] Film washing technique

> At 10:30 PM 5/2/2003 -0400, you wrote:
> >     Hi,
> >
> >      As a former professional, I can attest the Fresh
Hypo (not the type
> > that sits
> >   in the newsroom darkroom for a week without being
changed) will do the
> > job with
> >no surprises 10 down the line. But, since many of you
appear to be hobbyists
> >you might also want to check out the potential hazards
and be sure your
> >home darkroom is ventilated properly.
> Good advice about using fresh fixer and making sure you
have ventilation.
> >    Hypo i.e. Hydroquinone.
> >    This is the link to the NIOSH Pocket Guide to
Chemical Hazards
> No, no!  Hydroquinone is a developing agent.  Hypo is
slang for the active
> agent in fixer which is currently Sodium Thiosulfate.  Way
back when these
> things were getting their nicknames fixers used Sodium
Hyposulfate.  Or so
> I have been told by those who claim to remember <g>.
> David
  Sodium Hyposulfate was never used as a fixer. However,
what is now called Thiosulfate was thought to be
hyposulfite, hense the name. My 1938 edition of _Dictionary
of Photography_ still lists Hyposulfite as an alternative
name for Thiosulfate even though this use was dropped
decades before.
  The cation matters. Ammonium thiosulfate is the most
effective fixer, particularly for high iodide emulsions,
which includes most films. Sodium Sulfate is next. Potassium
thiosulfate is not a good fixer, working very slowly.
However, the current idea that developers with potassium
based alkalies in them will result in poor fixing is not
correct. Not very much potassium is carried over into the
fixer and I doubt if enough would react to cause a
detectible effect.
- ---
Richard Knoppow
Los Angeles, CA, USA