U of S | Mailing List Archive | alt-photo-process-l | Re: Paper negatives- Ink Selection

Re: Paper negatives- Ink Selection

Loris, my question was a simple question: on what are you basing
the statement that your exposure times are shorter than others'?
because I'm not seeing other gum exposure times in the thread, never
mind that even if there were, no valid conclusions could be drawn
from the comparison. Instead of answering the question by
pointing to posts I missed, or describing the data on which you base
the assertion, you simply repeated it. It's not a helpful answer to
the question, but I won't pursue it further; I'll take your word that
there are these people you know about, somewhere, who print exactly
as you print, with exactly the same emulsion, same paper, same light
source, same negative media and exact same working procedures (same
environmental conditions, we would also have to assume) who have to
use longer exposure times because they're using negatives with more
DR, or they're not calibrating, or their calibrations are flawed
somehow. This is quite a remarkable finding, as I've never met two
gum printers who use the same everything, unless they happen to be
taking a workshop together and are using premixed emulsions and all
other materials and equipment supplied by the teacher. Oh well, I
don't really care, I was just curious. Back to check on my print,

On Oct 14, 2008, at 11:08 AM, Loris Medici wrote:

Katharine, don't worry I'm pretty careful about this subject -
knowing (by
experience) you'll chime in every time it's brought up, to
clarify ;) I'm
getting older I guess; less and less surprises... ;)

I wasn't attributing the short exposure I'm using to curves at all,
was a side note (which should have been enclosed between parenthesis,
sorry). I was trying to say (indirectly) that since the DR (=density
range) and tonal progression of my paper negatives (made with the
HP 9180
all-inks grayscale setting, using the printer's plain paper
profile) are
close to ideal (in tricolor gum printing context - which is
supported by
the fact that the curve I devised for this particular combination
is the
smoothest and least dramatic one among all curves I did until now),
therefore, other people's longer exposure times could be caused by the
fact that they're using negatives with more DR, which naturally will
require more exposure and a stronger / more dramatic curve to
counterbalance. Or they're not calibrating, or their calibrations are

Hope it's clear, and makes more sense to you now. I perfectly
the confusion I may have caused on your part.


P.S. BTW, I have compared my times with the times of people who use
similar light source, emulsion, negative media and working
procedures. I'm
perfectly aware of the parameters affecting exposure time and pay
attention to them.

14 Ekim 2008, Salı, 7:18 pm tarihinde, Katharine Thayer yazmış:

Loris, I'm wondering what data you're basing this last bit on, that
other people's exposure times are longer than yours.   It's generally
not useful to try to compare exposure times because there are so many
variables involved, but putting that aside for a moment,  I've looked
back through this thread, and the only reference to exposure times I
can find is Guido's comparison between oiled and unoiled Epson PQ
paper, 8 vs 48 minutes, with cyanotype.  Since it was  cyanotype, and
since the paper is a heavier paper (27 pounds) than yours,  it's not
surprising that his exposure time for unoiled paper would be longer
than yours, and we haven't even got to light source yet;  to reach
immediately to curves to account for a difference in exposure times
seems rather a long stretch to me.

Perhaps I've missed other posts that included exposure times for gum
and paper negatives (my server doesn't accept some of the alt-photo
mail, so I don't always see all the posts).   At any rate, my times
with oiled paper negatives run close to my times with inkjet
transparencies, about 3 minutes,  to add to your database on exposure
times.  I don't have any comparison with unoiled paper to offer,
because that's not an option that makes any particular sense to me.

But be that as it may, I can't see any reason why curves would
account for a difference in exposure time.  After all, the exposure
time is determined before curves are even calculated, at least that's
how it is with the system I use, and I assume it's the same with all
systems; the curve doesn't change the exposure time.  Besides, curves
simply redistribute the tones within the print tonal range that
particular emulsion can print under that particular protocol; they
don't extend it, so there's no logical reason curves would have any
effect on exposure time.

On Oct 12, 2008, at 11:23 AM, Loris Medici wrote:

I use the grayscale using all inks (not black and gray - if present
- inks
only), plus, I choose plain paper as the media. Fortunately, with
my inks
the printer lays just enough ink giving an almost perfect
negative in
terms of density range (something around log 1.0), and the curve I
use for
gum prints are is the least drastic and most smooth one among my
collection for many processes and paper. In fact, I think that's
why other
people's exposure times are considerably longer compared to mines...