[LargeFormat] Help, scratches on negative..

[Frantisek Vlcek]

PC> Achal, the advice that has been given to you so far by Uncle Dick et. al. is
PC> excellent, however let me add one comment to your statement about washing.  
PC> You do not need "fast running" water.  What you do need is to change the 
PC> water periodically, with slight agitation (or constant preferrably) in 
PC> between.

PC> How you accomplish this depends on the method you decide upon for 
PC> processing.  If you are going to use metal hangers in a tank.  Then use the 
PC> same tank for washing.  I would think that 20 complete changes of water in 
PC> the tank, with 30-60 seconds of agitation in between, would result in fully 
PC> washed film.  You might be able to get away will fewer changes of water, but 
PC> it's better to err on the side of more and it depends on the quality of your 
PC> wash water.

PC> Regards, Pete

Hi,
   wrt washing - yes, running water is not actually needed. However,
   the best washing method is by turbulent washing - that is water
   from small jets spraying over the neg, that's what the big labs
   use(d), it saves water as well, and is the most efficient method,
   but hard to DIY... I normally use the Ilford Archival method for my
   negs of all sizes (no LF yet, though - I am still a lurker <g>),
   with about doubled the amount of steps, to be on the safe side.

   I can't omit to recommend some hypo clearing agent, it can really
   speed up the washing and make the negs more archival - I use plain
   DIY solution of sodium sulfate (200g per liter of stock solution)
   and sodium bisulfite (15g per liter), mixed together in 750ml tank,
   added water to make 1 liter, that's stock, it gets diluted 1:10
   for use. The bisulfite is simply a preserving agent for the
   sulfite, as the bisulfite oxidizes more quickly preventing the
   sulfite from oxidizing. What it does is it attaches to Ammonium
   thiosulfite salts in the emulsion and changes them to more
   easily washable salts, which wash more easily out of the emulsion.
   Of course it works only if you use rapid fixer, but nobody uses old
   acid fixers anymore, no? They are the worst for archivality anyway,
   it should be a crime using them for good negs <g> (it can form
   almost unwashable complexes with iodine salts, which you almost
   can't wash out). This clearing stuff works for thiosulfite fixers
   whatever they are for negs or papers, it's basically the stuff
   Kodak sells as hypo clearing agent (they add much more small
   quantities of some other chemicals to it, though). It's very cheap,
   just mix it in the open though (SO2 gas can be produced). It
   significantly changed my washing times. Also, it's proven that
   distilled water is not so good for washing, as the things
   in the water actually help washing out the salts in the emulsion. However,
   if you have too hard water, some deionizer would be probably good.

   A good but simple test for presence of any fixer salts (actually,
   just sulfite salts) in the washing water is to drop few crystals of
   KMnO3 (Hypermangan - the small crystals which make the purple
   disinfecting water solution, household chemical) into some water,
   and add some of the washing water - the solution of KMnO3 is
   purple, if there are any sulfite salts it instantly precipitates
   into yellow sediments or changes colour to dirty yellow. It's a
   dirty test though, without knowing exact numbers, but still useful.

   HTH,

Good light,
   Frantisek Vlcek