U of S | Mailing List Archive | alt-photo-process-l | Re: carbon transfer (mainly: digital negatives)

Re: carbon transfer (mainly: digital negatives)



Hi Phritz,
Just one thing to your remark of raising temperature to 50 degrees; i
used the rabbit glue -if you buy it by BOESNER i could be same stuff
you use- for preparing inkjet paper, and temperature is critical in
that sense that over 40 degree C blistering could be a problem.
What i read about it, was to raise temp. to 60 degree C and when
using it, go down to 40 degrees.
succes,
Henk


On 30 mrt 2009, at 14:01, phritz phantom wrote:

after a few weeks of trying, i finally get more or less acceptable
results. now it's time for the fine tuning.
i think most of my problems lie in the preparation of the digi
negs. i read in the sandy king article that carbon needs a more
contrasty neg that gum, so i printed a few small ones with the
"strong contrast (rgb)" preset of photoshop.
not the best of ideas, because it has too little shadow density.
the areas of the negative that have good density are those that
print rather well (f.e. the side of the car in the pic at the
bottom), but the thin areas are those that trouble me.
i have the same problem with gum occasionally. even though the
contrast range is not big, the dark areas often lack detail. how do
i get more guts in the shadows? alternativephotography seems not
to have a curve suggestion for carbon? how do you treat your images
before printing? curve or straight?

on a related note:
is it possible that photoshop loses shadow detail when inverting an
image? scatterbrained as i am, i often forget to invert an image
before printing it. this happened again a few days ago. so i
printed the same images again, only inverted. and compared there is
definitely more detail in the shadows on the positive on film than
in the neg on film. for example the stacked wood in the second pic,
in the shadow part i can see a little detail (very faintly the
pattern of the ends of the logs), while the same area in the
negative on film is completely blank.
my guess is that the printer can't print those very faint areas, so
they just get lost between photoshop and printer.

my last problem is that there is some kind of fogging, that only
seems to happen in the densest areas of the print. it's clearly
visible in the two scans (actually it's more visible than in the
original). i think it has something to do with the warm water
development. i think the excess gelatine comes off the shadow areas
first and later off the lighter areas, so those dark areas are
exposed to the warm water longer than the light areas. so more
pigment floats off and these cloud-like grey areas are produced.
i already tried raising the temperature of the warm water bath to
get a quicker development. i used appr. 50c (120F) in the second
pic (the one with the stacked wood), the grey fog is less, but not
completely gone.

and regarding relief:
if i want to have a more relief in the final print (i have pretty
much none right now - at least nothing tactile when sliding my
finger over the print). the clue to relief seems to be a thicker
tissue. but does it also mean, that i'd have to expose longer?

the two prints:
both are on homemade tissue (glop: 20gr rabbit skin glue + 15gr
sugar + 3.5gr lamp black (powdered) + 250ml water)
spirit sensitized with: 2x 4ml per 8x10 (20ml acetone + 20ml 2.5%
dichromate sol.)

http://i31.photobucket.com/albums/c367/phritz/02-1.jpg?t=1238414209
exposure: 1:30min; 2 min soak; 19 min press.


http://i31.photobucket.com/albums/c367/phritz/01-2.jpg?t=1238414270
exposure: 1:50; 2min soak; 27min press. the one with the increased
temp in the warm water.
(contrast is way off in this one)
both images are still inverted because i'm heading for double
transfer.

any ideas for improvement?
phritz