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

Marek Matusz marekmatusz at hotmail.com
Thu Mar 7 16:53:16 GMT 2013 

I use similar unit and my gum exposure is 1-2 minutes. It also seems like you are adding little pigment to your gum. Although I do not prints with this black so maybe i am off on it. Do yourself a favor and buy Chris's book.. A new gold standard for gum printing. I agree with Diane to mix new dichromate and use distilled water if you can. If you use reagent grade dichromate and keep solution in dark place they will last a while, at least a year or two in my experience.  

Marek

Sent from my iPhone

On Mar 7, 2013, at 10:39 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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