Good for you. I never had good luck fine tuning direct reversal negs. Plus
I always liked going from Fresson, a direct carbon that can use a straight
neg, to single transfer carbon, which requires a reversed neg and more
contrast, so the best solution has always been -for me- to make a positive
on 4 x 5 in. from which I could make any kind of neg I wanted, upside down
or not.
..
>I read your book and so I was realy surprised that it worked. Presensitized
>tissue 12 hours dried has the same amount of fog (which does mean nearly no
>fog!) than "normal" tissue sensitized later with a brush in a 3%-solution
>and dried in 90 minutes!
>The exessive developing time and the need of heavy agitation is regardless
>wether I use presensitized material or "normal" tissue with need for
>sensitizing step. The image starts to apear in correct density much earlier
>but I need agitation and prolonged developing to wash of the gelatin/pigment
>slime.
I think you are overexposing your pigment paper. Cut down exposure 30% or
so and see what happens.
>In every case I use fresh material and get best results with clear highlights,
>deep blacks and fantastic graduation in middtones and maximum densities
>as typical for carbon. My way seems to be more troublesome than yours,
>but I do not know why because its the same with "normal" tissue as I
>explained.
>
>How do you achive short drying times? I fear that higher drying temperature
>could cause fog or do you add a drying agent when coating presensitized
>emulsions?
During the cold winter here the air inside our homes tends to be very dry,
e.g., 30% RH or so. This is a problem as everything dries too quickly.
Thick gelatin coatings tend to break and you need a good vacuum frame to
keep everything into contact although as explained in my book -I think-
(not at hand and parts of it were written in the 70s...) too much pressure
can leave stress marks. Some humidifying of the drying room, around 40 to
45%RH is desirable, always at no more then 21 to 22C
In the steamy summers in the North Eastern part of America I like to
consider July and August as totally useless for carbon printing. When I was
teaching at the Maine Photo Workshop the promised air conditioning unit was
never available (year after year) and we ended up using acetone based
sensitizers, early in the morning, to get anything done. I think my book
also has other, alcohol based formulas. This was simply brushed on the
pigmented side of the tissue and it would dry in just a few minutes. It
worked well but occasionally you could see some brush strokes in the
prints.
In my own lab I would use an oscillating fan, on slow speed, in the drying
room and as long as RH was reasonable, i.e., below 60%, the suspended
tissues (with large "paperclips" to prevent the tissue from excessive
cockling as described in my book) would dry in a couple of hours.
Whether or not the pigment is presensitized, slow drying is to be avoided,
or else you are likely to have fog problems.
>Do you think that it is necessary to add glycerin and/or sugar to a
>presensitized emulsion whith will be processed soon after drying or could
>the dry gelatin crack without it?
For reasons explained above, it may be a matter of seasonal temperature. If
it is humid there is little need for it. If it is very dry you do need it.
>Another question of interest could be the permanence of gelatin. Good
>pigments (like boneblack) are nearly absolute permanent.
>But gelatin could turn to grey or yellow and this would change the prints
>color or (in theory) higher the contrast. Do you know anything about the
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Not in practice in my experience. Gelatin has been found in the pyramids of
Egypt. The product we have now, properly hardened, is much superior. In
years of accelerated testing of pigmented scales to test the lightfastness
of color pigments I have not seen damage to gelatin layers per se. I have
seen pigments advertised as "permanent" fade after just a few days and have
seen papers turn gray and yellow after just a few weeks, in which case the
*transparent* gelatin took on the gray/yellow color. In cases where I used
what turned out to be excellent papers and pigments, there was nothing
discernible after months of exposure 0,5 cm away from a fluorescent tube
turned on 24 hours a day.
Impure forms of gelatin, i.e., animal glue, has been used as a sizing agent
since the earliest days of papermaking. I have one "incunabulum" here in my
collection in excellent shape. For the two or three of you who don't know
what that is, an incunabulum is (according to one definition) a document
printed within the first fifty years of the invention of printing with
movable type, i.e., ca. 1450. Mine was printed by a Frenchman, Nicholas
Jason while he worked in Venice in 1477. This thing is 518 years old! Just
think for a moment what your Toyota will look like 515 years from now;-)
Just think what *you* will look like 500 years from now:-)
This five-century old paper is still strong, and very solid (I think that I
could fold it many times without breaking it although I wouldn't try it for
the sake of argument;-)) but is not bright white. I don't think it ever was
anyway. It was never bleached and it was not coated with a thick barium
sulfate (BaSO4) protective coat to keep its surface bright white like many
non-RC photo papers today. Elsewhere in my collection I have several
"modern", i.e. 20th century papers that are *dark* gray or yellow except
that the coated side where the illustration is, appears bright white just
like the RC paper you processed yesterday. Thanks to that protective
coating.
This being said, gelatin coated materials have to be hardened and even then
they do not enjoy very high humidity environments for long periods of time.
Nothing is immortal, except perhaps *certain* photoceramics. This will be
the subject of my next book
Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada