[LargeFormat] Printing the Giant Pinhole Negative: A Question

[Mike Kirwan]

You certainly have an interesting challenge. I do not know who you were
talking to at Ilford but the RC Multigrade Papers do have a developer
incorporated into the emulsion. In fact I have developed prints just by
dropping them into a bath of sodium carbonate. Weak but the image came up.

You also might be getting stains due to pooling of water between the the two
surfaces. I have never made a wet contact but have always let the paper
negative dry first. Maybe that is something for you to try.

Mike

-----Original Message-----
From: largeformat-admin@f32.net [mailto:largeformat-admin@f32.net]On
Behalf Of Guy Glorieux
Sent: Tuesday, June 04, 2002 7:45 AM
To: LargeFormat
Subject: [LargeFormat] Printing the Giant Pinhole Negative: A Question


Hi all,

This print is proving to be a much greater challenge than we ever
anticipated and new issues seem to surface at every step along the way.

This weekend, we thought we had solved every problem along the way and
we were ready to do the final print on Sunday.  But we've encountered
one last problem that has to do with a weird chemical reaction when
printing the wet paper negative onto wet unexposed RC paper (see further
on) and suggestions from the list are welcome.

The basic problem we had to solve after processing our giant pinhole
negative was the following: how do we make a contact positive of a 12.5
x 8.5 feet paper negative with substantial over-exposure in the center
and substantial vignetting at the edges.  This has raised much more
complicated questions than just preparing the basic room set-up for the
exposure and calculating pinhole size, f/stop and exposure time to
create the negative.

First, you need the physical place to print and process an image that
size.

Then you need to develop a lighting system that will both cover the
whole image and be heavily weigthed in the center to reduce the amount
of dodging and burning required by the negative.  You also need to find
a way of doing whatever residual burning and dodging with a light source
that is not single-directional (as is the case with an enlarger where
you have full control over edges) but spreads widely and makes you lose
control over edges.

You also need to find a way of changing contrast filters during the
exposure process (to deal with a negative that has large areas with
substantial differences in contrast) with the constraint that the light
source is 15 feet above the ground and you can't step into the print
with a ladder to change contrast filters.

Then you must make sure that the paper negative will stick face to face
to the surface of the paper being exposed so that you have a sharp image
all over.  This is normally done by wetting the negative and the
unexposed positive and squeegeeing them together emulsion to emulsion.

We thought we had pretty well solved every issue when we got together
this Sunday to print the real print.  But we encounterd a very weird
reaction of the unexposed paper when wetted to be squeegged to the
wetted paper negative.  The paper had lost about 1 full stop in
sensitivity and the positive had unseemly strains and stains all over.

After much head scratching and testing, we think we can solve this by
pre-washing the unexposed paper for about 30 minutes but I'd like to
know more about what it is in the unexposed paper that might be
responsible for this weird reaction.  The paper we are using is Ilford
Multigrade IV RC DeLuxe (Pearl).  Ilford says that the paper does not
have developer in the emulsion.

This is something I had never heard of before and I'd not encountered in
my own printing from paper negatives before.  But when doing tests with
standard size paper, we found that this happens when the unexposed paper
is left wet for several minutes before exposure and processing.

Any thoughts or suggestions are most welcome.

Cheers,

Guy


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