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 > > > > > > --- > > > Rollei List > > > > > > - Post to rollei_list@xxxxxxxxxxxxx > > > > > > - Subscribe at rollei_list-request@xxxxxxxxxxxxx with > 'subscribe' > > > in the subject field OR by logging into www.freelists.org > > > > > > - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with > > > 'unsubscribe' in the subject field OR by logging into > www.freelists.org > > > > > > - Online, searchable archives are available at > > > //www.freelists.org/archives/rollei_list > > > > > > > --- > > Rollei List > > > > - Post to rollei_list@xxxxxxxxxxxxx > > > > - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' > > in the subject field OR by logging into www.freelists.org > > > > - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with > > 'unsubscribe' in the subject field OR by logging into > www.freelists.org > > > > - Online, searchable archives are available at > > //www.freelists.org/archives/rollei_list > > > > > > > --- > Rollei List > > - Post to rollei_list@xxxxxxxxxxxxx > > - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' > in the subject field OR by logging into www.freelists.org > > - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with > 'unsubscribe' in the subject field OR by logging into > www.freelists.org > > - Online, searchable archives are available at > http://www.freelist --- Rollei List - Post to rollei_list@xxxxxxxxxxxxx - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with 'unsubscribe' in the subject field OR by logging into www.freelists.org - Online, searchable archives are available at //www.freelists.org/archives/rollei_list