These days, anyone attempting to use the rather difficult carbon transfer
process, which is perhaps twenty times more difficult than platinum
printing, is likely to work on not more than two or three images at a time.
Each image will have to be printed a few times before excellent results are
obtained.
It would take several pages of explanations to explain in great details
what I mean in the above paragraph and this is out of the question for me
at this time. I think most of it is covered in my books anyway.
>Pre-sensitizing
>also introduces storage problems. Non-sensitized tissue can be
>stored at room temperature for weeks and months on end with
>no appreciable deterioration,
Only under certain circumstances, with (1) the right pigment and (2) the
right paper base as a pigment support, (3) the right gelatin, and (4) the
right environment. If you have hit such a set of circumstances you are
lucky. I have had scores if not hundreds of letters here where it did not
work for many people.
In *many* cases it is difficult to manufacture a fog-free pigment paper
with a good shelf-life and this is one of several reasons why carbon is not
more popular than say, platinum.
> not the case with pre-sensitized tissue.
The pre-sensitized tissue has to be used within hours or else has to be
dried thoroughly and frozen solid.
>To Luis, I donUt understand your remarks about drying time. In
>normal working conditions there is no way I can get coated tissue
>to dry in 2-3 hours.
Normal? This is the problem with the Internet. I don't know whether you
live across the street from me or on the dark side of the moon... Normal
can mean +40C or -40C! Coated tissues in *my* lab (North Eastern part of
North America), if not in "my book" (not necessarily the one on paper;-))
requires a few minutes to get the gelatin to solidify and then, once
suspended with a gentle flow or air on the back of the 140 gram photo-grade
Schoeller paper I use, it dries quickly, especially in the winter months
>Perhaps you did not pick up on the fact that
>Stefan was pre-sensitizing his tissue? Certainly, if you were
>referring to the drying time after sensitizing I agree with your
>remark that the tissue should be used as soon as dry. I have conducted
> carefully controlled sensitometric tests with carbon tissue sensitized
>and exposed after completely dry at intervals of 1, 2, 4, 8, 16, 24, and
>48 hours and can assure all that sensitized tissue gains in sensitivity
>over time.
Absolutely in accordance with all scientific data published on dichromated
systems.
>The best procedure in my opinion is to expose the sensitized
>tissue at a precise time period, otherwise there is sure to be some
>difference in density.
Indeed and this can be dramatic with color printing where a 10% variation
on the (damned) cyan can be devastating. Monochrome work is much more
forgiving.
Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada