[alt-photo] Re: Gum Printing: Looking for some wisdom

Thu Mar 7 16:39:46 GMT 2013

Okay, Jennifer-- Well, I guess I'll just confess here and say that you lost
me after 'Base+fog.'  Once I got to the 'Macbeth 5 step grey scale,' I
somehow figured that this had nothing to do with my old English Lit classes.

So-- basically, you're over my head with all this talk-- and I should just
end the conversation here.  Nevertheless, the times for the other processes
(possibly with the exception of cyanotype, which also seems long to me)--
sound about right.  So I guess it's not the lights.  I'm not entirely sure
how 'off' dichromates get after several years-- but, yes, I would probably
mix new and go from there.

On Thu, Mar 7, 2013 at 11:28 AM, Darkrooms, Department of Art <
darkroommanager at cornell.edu> wrote:

> Diana,
>
> Thanks for your reply.
>
> I do use the unit for the other processes.  These are the exposure times I
> am getting for use with digital negatives:
> Cyanotype:  30 minutes
> VanDyke Brown: 10 minutes
> NA2 Platinum: 8 minutes
>
> I had the same feeling that I should not need such a long exposure and
> that over 10 minutes would be long.  I am starting to wonder if I should
> not be expecting to clear the Base+fog in one printing.  When I compare my
> time results test to a Macbeth 5 step grey scale 4 minutes is
> approximately the density of step two and 8 minutes is approximately step
> three.
>
> I should also add that I mixed the Potassium Dichromate 3 years ago and
> the Ammonium Dichromate 2 years ago.  Should I mix new?
>
> Best,
> Jennifer Gioffre
> Teaching Support Specialist
>
> Architecture Art and Planning
> Cornell University
> 120 Tjaden Hall
> Ithaca, NY 14853
>
> Office: 607-255-4207
> Fax: 607-255-3462
> jmg393 at cornell.edu
> darkroommanager at cornell.edu
>
>
>
>
>
>
>
>
> On 3/7/13 11:15 AM, "Diana Bloomfield" <dlhbloomfield at gmail.com> wrote:
>
> >Hey Jennifer,
> >
> >Other people will jump in here and surely have better suggestions for
> >you--  but just reading this over-- I would have said that your main
> >issue might be the lights (?). That seems like  extraordinarily long
> >times for exposure.  Maybe you're just doing a lot of testing, and I'm
> >just confused-- and whatever you're doing is way over my head-- but do
> >you use this same unit for the other processes you mention, with no
> >problems?
> >
> >Diana
> >
> >On Mar 7, 2013, at 10:58 AM, Darkrooms, Department of Art wrote:
> >
> >> Hello all,
> >>
> >> I have been following this list serve for about two months now and what
> >>a
> >> wealth of knowledge you all have!  I am hoping that you might give me
> >>some
> >> words of guidance as I attempt to tackle gum printing.  Before I ask my
> >> questions I would like to give a little background on how I will be
> >>using
> >> this process and where I amŠ
> >>
> >> I am the Photo Technician at Cornell University and we have been
> >>teaching
> >> an alternative processes course using Litho and digital negatives.  This
> >> past winter break I started using the quad tone rip and we are adding
> >>Gum
> >> printing to the list of processes covered.  I have had fantastic results
> >> creating negatives with Quad Tone RIP for Cyanotype, VanDyke Brown and
> >>NA2
> >> Platinum.  I am just starting the process with Gum and having only
> >>dabbled
> >> in gum briefly about 3 years ago I am getting a little tripped up with
> >>the
> >> process.
> >>
> >> So far I have completed the dot test that is outlined in the Keeper of
> >>the
> >> light to determine Pigment to Gum ratios for each color I would like to
> >> use.  I have completed this on both the Fabrino Soft Press (un-sized)
> >>that
> >> was discussed a few weeks back and Rives BFK sized in Gelatin and
> >>hardened
> >> with Glyoxal.  The dot test looked great and I am now moving on to
> >> determining a base time for printing with pictorico.  I am starting my
> >> tests with Winsor Newton lamp black 1/2g in 60ml of gum arabic mixed 1:1
> >> with  Potassium dichromate and another with Ammonium Dichromate.  I
> >> completed a time test with a strip of pictorico using 4 minute
> >>increments
> >> up to 32 minutes with each sensitizer on both Fabrino and Rives paper.
> >>I
> >> am using a homemade exposure unit that consists of a bank of closely
> >> spaced black light UV florescent tubes approximately 3 inches from the
> >> exposing area.  The tests on both papers took overnight to completely
> >> clear of the brownish coloring.  From what I have read some people are
> >> able to obtain an exposure on a light table in less then 10 minutes.  My
> >> tests show a distinct separation between the Base+Fog of the pictorico
> >>and
> >> the uncovered areas of the print up through 32 mintues.  On the Fabrino
> >> paper with Ammonium Dichromate at 32 minutes this difference is just
> >> barely noticeable and my thought is that at about 35 minutes I surpass
> >>the
> >> base+fog of the pictorico.  After about 12 minutes on all test some
> >> tanning is appearing.  If I were to go with a 35 minute exposure tanning
> >> is sure to be visible.
> >>
> >> My questions are:
> >> 1.  Should I try for longer exposures to see if I can obtain an exposure
> >> sufficient to hide the Base+Fog of the pictorico and if so is there a
> >> remedy to the tanning?
> >> 2.  Should I adjust my mix of sensitizer?  I have mixed the Potassium
> >> Dichromate in a way that it has a large amount of precipitated chem
> >>unless
> >> heated to almost 100F (this was done at a professor's request).  I mixed
> >> the Ammonium Dichromate as outlined in Sarah VanKeuren's Non-Silver
> >> Manual, placing chemical in a graduate to reach the 1oz line and adding
> >> water to 10oz.
> >> 3.  Or do you have any other suggestions?
> >>
> >> Thank you in advance for reading this long email and I am looking
> >>forward
> >> to any words of wisdom you have to offer.
> >>
> >> Best,
> >> Jennifer Gioffre
> >> Teaching Support Specialist
> >>
> >> Architecture Art and Planning
> >> Cornell University
> >> 120 Tjaden Hall
> >> Ithaca, NY 14853
> >>
> >> Office: 607-255-4207
> >> Fax: 607-255-3462
> >> jmg393 at cornell.edu
> >> darkroommanager at cornell.edu
> >>
> >>
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