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

Re: Paper negatives- Ink Selection

Keith, according to Loris's post below (which I didn't get) you use
saturated potassium dichromate for your sensitizer. The quickest way
to decrease your exposure time is to increase the dichromate;
saturated ammonium dichromate should cut your exposure time at least
in half. Also, humidity is correlated directly and strongly with
speed; I don't know what your climate is like there, but humidifying
your workspace would speed up your emulsion, if you wanted more
speed. Also, in my observation masa prints slower than other papers,
everything else being equal; that could be another consideration in
the length of your exposures.

There are so many variables affecting exposure time in addition to
those already mentioned (pigment concentration, for example) that
comparing exposure times isn't terribly useful, as I've pointed out

Since I didn't get Loris's post below, I'll respond briefly to it
here if you don't mind. Loris, thanks for answering my question. My
question, for the nth time, was "on what are you basing the assertion
that your exposure times are shorter than others'?" Okay, so you
base that assertion on the fact that your gum exposure times are
shorter than Keith's and Loris's, that's useful to know, and that's
all I was asking.

You seem to be suggesting that my "objection" (actually, I wasn't
objecting to anything, simply asking a question) was to your
statement that your particular printer settings, with your particular
printer, seem to be ideal for gum. I have no objection to that
statement at all; my question had nothing to do with that statement,
and I agree that the information could be useful to someone with that
printer (or perhaps not, since even individual printers of the same
make and model can differ on such variables). Your observation
simply underscores the obvious fact that different printers require
different strategies to achieve the best result. With my old
printer, the all-color greyscale produced a very nice gum print; with
my new printer, the colorized negative works better. But I wouldn't
think it was helpful to say that my very short exposure times must be
the result of my printer setting choices and that if other's exposure
times are longer, that must mean they aren't doing their calibrations
right, or aren't using the right printer settings, or whatever; since
there are so many other variables that affect exposure time, that's
simply not a conclusion that can be legitimately drawn. That's all I
was saying.

On Oct 15, 2008, at 8:43 AM, Keith Gerling wrote:

Hi Loris,

My gums require 15 minutes with oiled negatives.  I would really like
to reduce this.  Also, cyanotypes made with the same oiled negatives
require exposure times of 30-45 minutes.  How does this compare with
others?  It seems pretty long.


2008/10/15 Loris Medici <mail@loris.medici.name>:


AFAIK, Keith uses same gum (which he purchased in Istanbul from my
supplier), same stock gum strength, same negative media (18lbs
inkjet bond), same paper (Masa), similar light source (UVBL),
stronger dichromate concentration (saturated PD whereas I use 10%
AD) but
his exposure times are about 1.3 stop slower than mines (his 15
versus my 6:30 - oiled or non oiled negatives I don't remember),
which I
find remarkable.

Guido's cyanotype exposures with oiled Epson PQP are 8 minutes,
whereas my
exposure times are 9 - 12 with "Pictorico" which should be way
faster than
oiled Epson PQP (see Guido's Arista exposure times for instance).
We use
similar light source (UVBL), even exactly the same lightbulbs
TL'K40W). And I find this remarkable too. (I print Cyanotype using
colorized negatives BTW, not grayscale.)

Those were the facts / starting points that made me curious /
think about
and realize / assert what you seem to object.

Most importantly, I know a guy named Loris, who's printing using
the same
parameters (printer, media, paper, emulsion, working conditions
and work
flow ect. ect. - you name it) except for the fact that he uses
negatives made on Pictorico using premium glossy photo paper profile,
calibrated for cyanotype - which prints very well with gum with much
better shadow separation (blacks are comparable), but then his
times are considerably longer than mines (who's printing all-inks
grayscale negatives on translucent inkjet bond).

You somehow doesn't like exposure times comparisons, but if we didn't
share & compare exposure times (considering working conditions /
procedures) and be curious about them, I wouldn't realize this (which
actually should be obvious since I actually tested it, not

Now all this was because I said "HP9180 all-inks grayscale
negatives are
perfect for tricolor gum" (to remind the main topic / the actual
I've made), which is definitely useful information for those who
have that
printer (which is very nice also for making stable, high quality
color or
monochrome inkjet prints), unobjectionable to me until someone
else proves
it wrong and/or comes with a better way (read as: less exposure
time and -
not necessary - richer tonality) to do it.

So, if someone uses that information to get better results than
what they
were getting before, then this is good info for them. If I'm
proven wrong,
then that's good info to me since I'll learn an even better way to
do it
(by asking them / questioning causes). A good example to win-win

Hope that's even clearer for you,

P.S. Again, if we weren't talking about exposure times -> we wouldn't
arrive to that conclusion (even if you don't buy it). Most
importantly, we
wouldn't talk & think about reasons because we would dismiss /
ignore the
exposure times stated by others -> "knowing it's nonsense to
That's my second point. (To remind again, first point is: HP9180
grayscale negatives are perfect for tricolor gum...)

15 Ekim 2008, Çarşamba, 12:05 am tarihinde, Katharine Thayer

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
if there were, no valid conclusions could be drawn from the
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
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
equipment supplied by the teacher. Oh well, I don't really care,
I was
just curious. Back to check on my print, kt

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, that
was a side note (which should have been enclosed between

sorry). I was trying to say (indirectly) that since the DR (=density
range) and tonal progression of my paper negatives (made with the HP

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
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


Loris, I'm wondering what data you're basing this last bit on,

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

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
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
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 -


only), plus, I choose plain paper as the media. Fortunately,
with my


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 curves
collection for many processes and paper. In fact, I think
that's why


people's exposure times are considerably longer compared to
mines... (!?