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Re: [APML] Letter to Kodak.
Jason,
Just a thought to avoiding the problem with Tech Pan is to buy a 100 ft roll
of 220 (B&H has it in their catalog about $80), hyper a section of it and
roll in onto a fresh 120 backing. It means a bit of dark room handling.
I'm guessing that the imprint from the backing is due to the temperature of
hypering, so using a backing that has never been warmed should work. Once
you find a 120 roll backing that works, you could use it again and again.
Don
>
> To be sent tomorrow, FYI.....
>
> > Dear Pete
> > Please find enclosed a sample of tech pan as we disused.
> >
> > Here is the background:
> > Astrophotographers have been hypersensitizing tech pan successfully for
many years. Around 1998 (or so) we started noticing a problem with the 120
version. After hypering and developing we found a mottling effect along with
what appeared to be the frame markings transferred to the film. A call to
Kodak at that time revealed that the ink had been changed and that a backing
change should fix the problem and indeed it seemed to. For a couple of years
the new backing did its job and we were able to hyper and use the film with
excellent results.
> >
> > Fast forward to 2002. In preparation for a star party in May, I hypered
several rolls, some of which I had stored in the freezer and some I had
purchased from a dealer in Dallas. After exposing and developing the film I
found that the rolls that had been recently purchased showed the mottled
effect along with the frame number transfer, although it was not as bad as
what we experienced in 1998. Further investigation showed that the rolls I
had stored in my freezer were of the same emulsion batch as the dealer's (I
had purchased it from them about a year before). He had stored his at room
temp.
> >
> > I had not done much with the film in the last couple of years but would
like to begin using it again in a 120 roll back I have for one of my
telescopes. Last summer I ordered 10 rolls from Adorama and found it had the
same problem. Thinking that I again had received old film I requested two
sample rolls from Kodak and received them on Friday, May 7, 2004. I hypered
one of them and found the same problem.
> >
> > I have enclosed several samples as follows:
> >
> > 1) Unused box, emulsion number: 0451061 received from Kodak on May 7.
> > 2) Unexposed, hypered roll as follows..
> >
> > Unrolled in total darkness and placed on a reel. Exposed to
high-vacuum for 2.5 hours.
> > Hypered at 50 degrees
> > Centigrade for 36 hours. 80%N2, 20%H2 Forming gas. Re-rolled.
> >
> > 3) Short strip of #2 above unexposed, developed for 8 minutes D19 at 68
F.
> >
> > 4) Sample strip from emulsion number 0461001 UNHYPERED, developed
D19 for 60
> > minutes at 68F. NOTE that this batch, when hypered, shows the same
effect.
> >
> > From the samples above I have the following theory...
> >
> > 1) As you can see from #4 sample that extreme development of UNHYPERED
120 Tech Pan
> > does not show any mottling effect or frame data transfer.
> >
> > 2) On the other hand 120 tech pan HYPERED shows the effect.
> > I believe that the ink is indeed being transferred to the emulsion
after manufacture
> > while being stored. If the user is lucky enough to get a very
fresh batch
> > (only days old perhaps?) then freezing may stop the transfer.
> >
> > 2) I believe that the ink, in the emulsion does not affect normal use,
however prevents the
> > forming gas from penetrating the emulsion and therefore reduces
the hypering effect. Note
> > that the frame data and words "Kodak" show as LIGHTER than the
hypering induced base
> > fog.
> >
> > Questions:
> >
> > 1) Can Kodak change its manufacturing process to prevent this?
(different ink?)
> > 2) If not can the users obtain tech pan without the backing (to be added
after hypering)?
> > 3) Is there a way to "clean" the film before vacuum and hypering?
> >
> > Thank you for looking into this and I hope you can help us find a
solution. Many astrophotographers have all but given up using this wonderful
film.
> >
> > Regards,
> > Jason Ware
>
>
> --
> -Jason Ware
>
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