[alt-photo] Re: Gum Printing: Looking for some wisdom
jack at jackbrubaker.com
Thu Mar 7 17:13:43 GMT 2013
Just for amusement, I have used 30 year old AD solution with no
apparent problems. That is I got good prints. However I should qualify
that by saying that was with my working in a very loose manner that
would shock many on the list who carefully measure and keep records.
It was a saturated solution with precipitation at the bottom.
On Thu, Mar 7, 2013 at 11:58 AM, Diana Bloomfield
<dlhbloomfield at gmail.com> wrote:
> P.S. I'll second the suggestion that you should by Chris's book-- a wealth of information. And my exposure times for gum are typically 4-7 minutes.
> On Mar 7, 2013, at 11:53 AM, gumprint at gmail.com wrote:
>> Greetings Jennifer,
>> I have been making gumprints using a bank of 6 BLB 4" from the contact
>> frame with both analog and digital negatives. My exposure time range from
>> 30 seconds to 7 minutes, never more.
>> In looking at your pigment dilutions I found them to be much different from
>> what I have been using (since 1978). I am one of those people who tested
>> all the Windsor and Newton tubed pigments (with dichromate) to determine
>> staining and maximum pigment ratios. An emulsion made with 1/2 gram to 60
>> ml of gum arabic is, to me, quite dilute. For lamp black I would typically
>> use 1/2 gram to 10 ml of gum mixed 1:1 with a 15% solution of ammonium
>> dichromate and use Fabriano Artistico (post factory sized) or Soft press
>> FA. (I have to admit here that I never use WN lamp black because for me it
>> stains when over 1/2 gram and at 1/2 gram it is too thin.) I develop in 80
>> degree water for 15 minutes (face up for one minute first), changing the
>> water 4 times for total of 1 hour.
>> As an aside, nearly all the pigments I use are 1/2 gram to 1 gram per 10ml
>> gum, which I mix using a glass mortar and pestle so I am sure the pigment
>> is in suspension. There are a lot of variables in printing gum and some of
>> what you have not said may also be leading to your unusual results such as
>> development water temperature, length of development, humidity, coating
>> method and thickness, etc.
>> If your dichromate is dropping crystals it is likely over saturated. 30% is
>> a saturated solution with ammonium dichromate and it will drop out if under
>> 65 degrees. I would warm it in a hot water bath, not heat it directly.
>> With regard to the tanning effect, I think you may be seeing the gum arabic
>> that has been rendered insoluble from the lengthly exposure.
>> I hope this helps. Feel free to write back if any of this is unclear.
>> Carole Hollander
>> On Thu, Mar 7, 2013 at 10:58 AM, Darkrooms, Department of Art <
>> darkroommanager at cornell.edu> 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
>>> 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.
>>> 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
>>> Alt-photo-process-list | http://altphotolist.org/listinfo
>> *Carole Hollander*
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