[LargeFormat] A better way

[Richard Knoppow]

At 09:42 PM 08/07/2002 -0700, you wrote:
>Man - you learned a lot!  With a bit of time, you'll be able to sort it
>out and unlearn half of it ;-)
>
>JOBO print development takes place in a simple cylinder - the paper back
>hardly gets wet.  Film has what's called an anti-halation layer on the
>back side (keeps light from bouncing around inside the film and causing
>"halos" around highlights).  This layer needs to be dissolved and
>removed during development, so film must be held in a position such that
>chemistry can circulate around it.  You actually can develop film in
>print drums, but you'll most likely have to rewash the film after
>processing - too much chance of damage for my tastes.
>
>The CPP is physically large enough to process an 11x14 print, but JOBO
>doesn't make a drum to hold anything larger than 4x5 for that unit (drum
>diameter is the limiting factor here).  The PRO drum looks kinda like
>the bullet holder in a revolver, where each piece of film sits in its
>own chamber.  This unit is about ten inches in diameter, hence the need
>for a larger processor.   The large diameter is the reason that JOBO
>suggests the use of an air pump to lift the lid - it's hard to get much
>leverage with your thumbs, though it apparently can be done.
>
>Good luck,
>
>Karl Wolz
>
Previous stuff snipped...
  The anti-halation backing on most B&W film is a dye in the anti-curl
gelatin coated on the back of the support. It is not removed but
decolorized by the developer. The fixer usually will decolorize it too, but
more slowly. 
  Color films, and some B&W films have the anti-halation layer coated under
the emulsion next to the subbing. Again, its decolorized by the developer. 
  Now, you are correct that the back coated anti-halation dye will remain
if the processing solutions can't get to it. Color film doesn't have this
problem. 
  AFAIK, the only backing which are actually removed are the Remjet
backings used by Kodak on Kodachrome and many motion picture films. This is
designed to be blown off using a water spray at the entrance to the
processing machine. 
----
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com