Archived posting to the Leica Users Group, 2005/11/23
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I just use plain water which seems to work fine. --- Steven Keirstead <keirst@fas.harvard.edu> wrote: > >From what I have read, a long time ago Kodak and > other manufacturers had different gelatin and > film bases that were not as cohesive as modern > films and emulsions. The gelatin was softer, > weaker and could tear more easily. Sometimes when > the developing film went from a carbonate > buffered developer into an acid stop bath, CO2 > was formed by acid-base reaction from carbonate > and the effervescence in the would tear gelatin > specs off the film base, leaving a clear spot in > the negative. This would be more likely to happen > if the temperature was above 68?F (20?C) for the > process solutions. Modern films have pre-hardened > gelatin, so this is less likely to happen now, > unless you are working in tropical temperature > conditions. > > If you are making your own developer solutions, > you can switch to a Borax or Borate buffering > system, which will not effervesce. There may be > commercial developers with Borax buffer, but I > don't know of them. > > While there may be some developers that are > acidic or continue to have some activity in acid, > most are still carbonate buffered, and the pH > change and developer dilution of putting film > into a stop bath ensure a precise end to > development, while water alone may allow more > continued development. I usually use a 1.5% > Citric acid stop bath. A 15% (or 30%) Citric acid > stock solution seems to be quite stable, does > appear to grow microbes, does not smell like > acetic acid and is quickly diluted 1:9 from 15% > (or 1:20 from 30%) for working stop bath. > > > >At 04:05 PM 11/22/2005, Henning Wulff wrote: > > > >>The main problem is that pinholes can develop. > >>If you do use any 'stop bath', dilute it a lot. > >>... > > Richard <richard-lists@imagecraft.com> wrote > > >What exactly are pinholes? Actually holes in the > negatives or the emulsion? > > > > -- > ______________________________________________________________________________ > Steve Keirstead > Research Assistant II, Biology Teaching Labs, > Harvard Science Center, Room 409, 1 Oxford Street, > Cambridge, Ma 02138. > Work Phone: (617) 495-2683 , FAX: (617) 496-9105 > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for > more information > __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com