[LargeFormat] A better way

[Richard Knoppow]

At 09:39 AM 08/08/2002 -0700, you wrote:
>
>>   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. 
>
>AH!  This might explain something I found curious this year.  A friend had
>shot some Fuji Neopan 1600 (35mm), had a lab process the negs, and brought
>it over to my darkroom to make some prints.  I was somewhat surprised to see
>that the base of this film was very clear, not the usual grey.
>
>Six months later, I had a reason to shoot some of this film for the first
>time, and was startled to find that when I processed it (in ID-11), it had
>the usual grey colour in the unexposed areas.  Could it be that the lab had
>chosen a developer/fixer combination that produces that clear-base look?
>
>This could be a potentially useful bit of knowledge. There are some projects
>in the back of my mind for making b&w slides from negs, using a slide
>copier.  Knowing how to pick a developer to remove that colour cast would be
>great!
>
>So, if you have more details on this, Richard, I'd be delighted to hear
>about it.
>
>Cheers,
>\donw in Victoria
>
   I didn't think of it before. You can check if this gray color is fog or
dye by taking a scrap of the film and putting it a highly alkaline bath. A
little stock Dektol will do. If its residual dye it should disappear very
quickly. ID-11 and D-76 are not very alkaline compared to some other
developers which use carbonate or metaborate rather than borax. 
----
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com