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

Thu Mar 7 16:44:02 GMT 2013

Diane,

Thanks again.  I think that I will try mixing some new Ammonium Dichromate
and doing another test.

When I refer to the Base+fog, I am looking for the point where you can't
see a difference in the print density between the area with film and
without film.

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 11:39 AM, "Diana Bloomfield" <dlhbloomfield at gmail.com> wrote:

>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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