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

[Diana Bloomfield]

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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