FotoDave@aol.com
Thu, 21 Oct 1999 20:49:22 -0400 (EDT)
In a message dated 10/21/99 2:15:30 PM Pacific Daylight Time,
wallen@boulder.nist.gov writes:
> The thing that
> would worry me however, is the possibility of the grooves causing
> scratches. I've built a couple tubes out of ABS pipe, and even with the
> factory smooth walls I've noticed some slight abrasion on the back of some
> test sheets.
Hi Wayde,
Jobo also warns that by using their print drums to process films, one might
get scratches from time to time. I never had any problem.... not that I have
examined it very closely but mainly because it hasn't given me any problem in
the final prints. Dusts give me more problem than scratches on the back of
film, if there is any. I guess since we are using diffused light source, even
if there is small scratches on the back, the light gets diffused when it
reaches the emulsion, so it might not be that noticable.
> Another thing I wonder about adding bumps, grooves, or whatever to the
> tube, is whether the added work is a help or a hindrance. For instance,
> would it be possible for the solutions to cleanly remove the antihalation
> coating from the back of the film everywhere but where the bumps or groove
> ridges touch the film?
The bumps work fine. Withouth the bumps, I get problem with anti-halation not
clearing completely. When I switched to print drums with bumps (or ribs), I
thought that maybe the anti-halation dye might clear for the most part but
there might be some problem along the ribs. Turned out that that wasn't the
case at all. It perplexed me for a while, but now I think the reason is water
(or chemical) is able to go to the area beside the bumps, and as the drum
rotates, the water passes through the bump and probably lift the film up a
little and then put it back, so the whole back area get cleared of the dye
very nicely.
Pyro users have reported unevenness on the ribs area. I suspect that since
most pyro developer are quite diluted, agitation is very critical, and this
increased in agitation along the ribs might cause different development.
I don't know if grooves will work though.
Dave S
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