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

Diana Bloomfield dlhbloomfield at gmail.com
Thu Mar 7 16:56:02 GMT 2013 

Hey Jennifer,

I'm guessing with a new batch of dichromate, you might see a difference.  Definitely report back with your results.

Thanks, too, for the clarification on the Base+fog dilemma.  I guess I should be more concerned with that type of thing, but I admit, it's something I never ever thought about-- so I don't know.  Now I feel like I should be worrying.  I have so much other stuff to worry about, though, so I'm just not gonna think about it.  ;)

Diana

On Mar 7, 2013, at 11:44 AM, Darkrooms, Department of Art wrote:

> 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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