[rollei_list] Re: was Rollei Retro Film now is Rodinal pin holes

  • From: Peter J Nebergall <iusar4s@xxxxxxxx>
  • To: rollei_list@xxxxxxxxxxxxx
  • Date: Mon, 25 Feb 2008 14:14:48 -0800

The only time I have ever seen pinholes on 6 x 6 cm(as opposed to
airbells -- preventable by a good pre-soak) is on film that sat out for a
long time in extremes of weather.

P.J. Nebergall
On Mon, 25 Feb 2008 06:56:12 -0800 "Richard Sintchak" <rich815@xxxxxxxxx>
writes:
> I develop Acros in Rodinal often and have never seen any pinholes, 
> nor with
> any other films I've developed in Rodinal. Have you tried just using 
> a plain
> water stop bath and see what happens?  I have not used a Stop Bath 
> solution
> other than water for something like 10+ years.  It works just fine.
> 
> Richard S.
> San Francisco
> 
> My Commute Photo Blog
> http://shootingonthefly.blogspot.com/
> 
> My Flickr Page
> http://www.flickr.com/photos/rich8155/
> 
> 
> 
> On 2/25/08, Dennis Purdy <dlp4777@xxxxxxxxxxxxx> wrote:
> >
> > Richard, or anyone,  do you know what exactly is the cause of pin 
> holes
> > in film?  I have tried to research it and find a lot of 
> recommendations
> > to avoid stop bath and then I read opinions that stop bath don't 
> really
> > do it.  I have just processed some ACROS in Rodinal 1:50 and it is
> > beautiful but has lots of tiny pin holes.  I use this film a lot 
> and
> > have never encountered pin holes before, processing in XTOL or 
> Beutlers
> > or R09.  Are pin holes somehow created in development?
> > thanks if you know and even if you don't
> > Dennis
> >
> >
> >
> >
> > >
> > >      There seems to be a cult about alkaline processing.
> > > This is at least partially based on a mis-understanding of
> > > how hardeners affect washing.
> > >      First of all, hypo does not need to be acid, the acid
> > > is required by the commonly used white alum hardener
> > > (properly potassium aluminum sulfate). Alum works when the
> > > pH of the bath its in is within a certain pH window.
> > > However, hypo, either sodium or ammonium (rapid) type will
> > > work at almost any pH.
> > >      Now, why should fixer be acid if its needed only for
> > > the hardener?  There are a couple of reasons. One is that
> > > developer can't operate in a strongly acid bath. So, in
> > > order to insure development is stopped at a definite point
> > > one must use an acid stop bath followed by an acid fixing
> > > bath. A water wash does not stop the development right away
> > > and simply rinsing the film in water leaves quite a lot of
> > > developer in the emulsion. For paper on untreated paper
> > > support (so called fiber base paper) the paper base will
> > > soak up a lot of developer and carry it over to the stop
> > > bath and fixing bath. A definite wash step is needed if an
> > > acid stop bath is not used to deactivate the developer.
> > > Actually, there is some chance of staining in a water stop
> > > (not very great) because the developer continues to work
> > > without only the carried over sulfite to prevent reaction
> > > products from forming. In any case an acid stop bath
> > > followed by an acid fixing bath, with or without hardener,
> > > prevents a lot more problems than it causes.
> > >      Now, about washing. It was found long ago in research
> > > carried out at Kodak and at Agfa that emulsion treated in an
> > > acid hardening fixing bath washed out much more slowly than
> > > emulsion treated in a neutral or akaline bath. The retarding
> > > of washing rate was especially noticable when a white alum
> > > hardener was used. Kodak experimented with comparing fixing
> > > baths with white alum to fixing baths with chrome alum
> > > (potassium chromium sulfate). Chrome alum (a misnomer since
> > > there is no aluminum in it) must operate at a much lower pH
> > > (much more acid) than white alum. Even so it does not show
> > > the strong restraining effect on washing of white alum. So,
> > > Kodak concluded that there was something specific about
> > > white alum which was causing the effect. In fact, there are
> > > two things happening: one is that white alum, when in an
> > > acid condition, acts to bind thiosulfate and
> > > thiosulfate-silver complexes, the later the result of the
> > > fixing process, to the image silver and to the gelatin. The
> > > bond is quite strong so washing out of these materials is
> > > made much longer. The second effect is from the acid itself.
> > > Gelatin is what is called amphoteric, that is, it has no
> > > definite pH of its own. It takes on the characteristics of
> > > whatever bath it was in last. That is, if treated in an acid
> > > bath it acts like an acid and if treated in an alkaline bath
> > > it behaves like an alkali. However, gelatin _does_ have a
> > > preferred pH. This is called the isoelectric point and has
> > > to do with the way the gelatin was manufactured. For most
> > > photographic gelatin the isoelectric point is just on the
> > > acid side of neutral. The term isoelectric comes from the
> > > fact that the net electric charge on the molecules of the
> > > gelatin is neutral when its at this point. This is important
> > > to washing because the thiosulfate ions and those of the
> > > fixer reaction products carry a charge such that that are
> > > attracted to the gelatin when the gelatin is more acid than
> > > the isoelectric point and repelled from it when the gelatin
> > > is more alkaline.
> > >     It also turns out that white alum looses its hardening
> > > effect if the gelatin is made too alkaline but will retain
> > > most of it when its about neutral.
> > >     It was discovered in the early 1930's at both Kodak and
> > > Agfa that treating film or paper in an alkaline bath after
> > > fixing but before washing would much accelerate washing.
> > > However it would also destroy the hardening effect. Various
> > > substances were suggested, sodium carbonate (agfa) ammonium
> > > carbonate, Kodalk, even Borax (Kodak) all at around a 2%
> > > concentration. All work but none preserves the hardening
> > > action.
> > >     Sometime before 1900 it was discovered that sea water
> > > was more effective in washing than fresh water but the
> > > reason was not known. It was known that a fresh water rinse
> > > had to follow the sea water wash if the images were to be
> > > permanent. When sea water washing became imperative during
> > > WW-2, especially for ship board operation extensive research
> > > was done for find the reason for the effect.
> > >     Kodak discovered that it was partly due to pH but mostly
> > > due to the ion exchange properties of some of the salts in
> > > sea water. After considerable research Kodak discovered that
> > > the most effective salt was a sulifite, the cation not being
> > > particularly important. From this Kodak developed Kodak Hypo
> > > Clearing Agent. This consists of about 2% sodium sulfite
> > > buffered to neutral with sodium bisulfite and containing two
> > > sequestering agents. Kodak found that at neutral pH, as
> > > provided by this bath, the binding effect of the acid due to
> > > electrical charge was broken (the pH being below the
> > > isoelectric point), the pH was outside of the window where
> > > white alum has binding action on fixer and its reaction
> > > products but is NOT outside the pH window where the
> > > hardening cross-linking is undone. In addition sulfite has a
> > > specific ion exchange affinity for thiosulfate and its
> > > silver complexes. So, by its use washing is accelerated even
> > > beyond the rate yielded by a simple akaline bath and the
> > > rate does not depend on the pH of the fixing bath or on
> > > whether it has alum hardener or not.
> > >     The sequestering agents, sodium citrate and EDTA
> > > tetra-sodium salt, are present for two reasons: one is to
> > > prevent a deposition of aluminum salts from the hardener on
> > > the surface of the film or paper, the other is to hold in
> > > suspension any mineral impurities in the water (mostly the
> > > magnesium  and calciumcarbonate consitituting the "hardness"
> > > in water which would also form hard-to-remove deposits).
> > >     Since this wash aid is capable of un-binding some
> > > incompletely converted fixer reaction products it also has
> > > the effect of increasing fixer capacity a bit.
> > >     In any case, when such a wash aid is used there is
> > > absolutely no advantage of a non-hardening or a non-acid
> > > fixing bath.
> > >     Even though some modern B&W films have very hard
> > > emulsions not all do and there is still some advantage to
> > > the hardener in preventing damage to the film when its wet
> > > (the hardener has little or no effect on dry film).
> > >
> > > ---
> > > Richard Knoppow
> > > Los Angeles, CA, USA
> > > dickburk@xxxxxxxxxxxxx
> > >
> > > ---
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