U of S | Mailing List Archive | alt-photo-process-l | Re: Gum calibration (was: Paper negatives- Ink Selection)

Re: Gum calibration (was: Paper negatives- Ink Selection)

Hi Loris,

I'm using an Epson 7600.  I would like to try printing colorized
negatives, but have never gone there because it has never printed
yellow. (this printer was given to me in this condition) The head must
be totally clogged as I've tried everything to no avail.  (If anyone
has any suggestions, I'd appreciate hearing them.) In any event, I'm
using a non-Epson ink and only using ink from the black cartridges.
The paper setting that I use is one that is intended to print on Tyvek
- for banners and the like.  I was looking for the least amount of
ink, and I figured that this setting - as Tyvek is nonabsorbant -
might do the trick.  To be honest with you I never really did much
testing of the paper profiles.  The 7600 driver has many and I was a
bit overwhelmed.  Which setting do you use?

Curves.  Yes, I should be testing curves.  There's no excuse.   With
Mark's proximity I COULD sit outside of his door and hound him with
questions whenever he comes up from the basement (which I'm assuming
is now seldom due to his new press?).   The step tablet results I get
on masa with a no-curve output is very acceptable with oiled negs (not
so much with non-oiled) but I never looked at the curving/PDN process
as a means of reducing printing time.  Maybe I should.

I appreciate the advice.  I'm very excited that in two weeks I will be
picking up a NuArc light source from a fellow list-member.  I'm hoping
it will be faster!  Perhaps I will use this new light as an
opportunity to do things correctly?  I'd be very interested in seeing
a snapshot of one of your un-oiled negs, if that would be possible.
Just something that give me an idea of your range of tones.

As for the personal lubricant suggestion, I'll let someone else take a
crack at that.

2008/10/17 Loris Medici <mail@loris.medici.name>:
> Hi Keith,
> What printer / ink and paper profile settings are you using? If you're
> using grayscale negatives (which in your case could be giving more than
> enough density range for gum), then you may switch to colorized ones which
> are calibrated to give just enough DR!? (If that's the actual reason of
> your relatively longer exposure times, of course...)
> If I remember correctly, you weren't using curves, right? You have someone
> very very competent in making digital negatives, who's living very close
> to you ;) Why not asking them? (If you haven't already + If the current
> exposure time is unbearable to you and/or you feel that you need to make
> some improvements... Not to my eyes though!)
> Maybe you can calibrate for a pre-determinated printing time (which you
> find is bearable) such as say... 7:30 (1 stop faster) for your case, which
> gives you a strong enough gum layer (has to be tested of course), then
> fiddle with your working parameters (coating solution, curve, development
> ect. ect.) to suit that printing time. It's right the opposite of the
> usual (which is to determine the standard printing time for "a particular
> coating solution + particular working parameters" with step tablet tests,
> then design the curve based on that). I find the usual approach equally
> awkward compared to what I just suggested -> with gum it's hard to be such
> consistent, to test every possible coating solution, and why in world
> would I want to leave aside all that flexibility provided by the process?
> Any thoughts? (Especially to Mark, Michael, Christina...)
> BTW, as a last note: if Keith's slow coating solution speed is due to low
> humidity in his working environment, can adding glycerin (or propylene
> glycol) to the coating solution (which are humectants) help to keep
> moisture? Are dichromates and glycerin (or propylene glycol) compatible?
> If not, then these additives could also help to thin the emulsion a little
> bit (for better spreading), not to the extent water does. Plus, as an
> added bonus,  since they're part of personal lubricants (I imagine Mark
> making funny jokes here), I think they may also help in case of grabby
> paper like Masa? :))
> Regards,
> Loris.
> 15 Ekim 2008, Çarşamba, 6:43 pm tarihinde, Keith Gerling yazmış:
>> 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.
>> Keith