[Alt-photo] Gum pigment mixed in batches

David Robertson david at robertson.yt
Tue Jan 9 14:18:33 UTC 2018


I’m yet to make my first GB print, but I am familiar with dichromated gelatin holography plates. These are sold unsensitised because the reaction does happen slowly in the dark.

David

> On 9 Jan 2018, at 13:52, Jim Patterson via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org> wrote:
> 
> Hi, yes the dichromate will react and harden the Gum even in the dark.  This is called the dark reaction.  It is slower than when exposed to UV light.  Coated paper, even in the dark will slowly harden like it was exposed to sunlight.
> 
> Sent from my iPhone
> 
>> On Jan 8, 2018, at 11:50 PM, Francesco Fragomeni via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org> wrote:
>> 
>> Interesting, hadn't heard that before. Thank you.
>> 
>> Can anyone else weigh in? Does anyone do this without issues or has anyone
>> tested this to confirm whether or not the solution will desensitize/change
>> with time?
>> 
>>> On Mon, Jan 8, 2018 at 9:28 PM, Denny <dspector at charter.net> wrote:
>>> 
>>> My understanding is that the dichromate will react with the gum (slowly)
>>> in the dark, though I’ve never bothered to test this.
>>> 
>>> 
>>> 
>>> *From:* Francesco Fragomeni [mailto:fdfragomeni at gmail.com]
>>> *Sent:* Monday, January 08, 2018 9:12 PM
>>> *To:* Denny
>>> *Cc:* The alternative photographic processes mailing list
>>> *Subject:* Re: [Alt-photo] Gum pigment mixed in batches
>>> 
>>> 
>>> 
>>> Sorry, I might have been unclear. I mean specifically mixing premixed
>>> emulsions i.e. pre-mixed gum arabic, dichromate solution (i use 13%), and
>>> watercolor pigment. I'm asking if I can premix the complete ready-to-coat
>>> sensitized solution in batches.
>>> 
>>> 
>>> 
>>> You mention not to add the dichromate but why would that be? Does
>>> dichromate lose sensitivity or go bad after its been mixed?
>>> 
>>> 
>>> 
>>> On Mon, Jan 8, 2018 at 8:54 PM, Denny <dspector at charter.net> wrote:
>>> 
>>> Francesco,
>>> 
>>> I routinely mix gum and pigment in large batches and I've had no problems.
>>> Just don't include any dichromate,  and mix well before using each time.
>>> 
>>> Denny
>>> 
>>> 
>>> -----Original Message-----
>>> From: Alt-photo-process-list
>>> [mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf
>>> Of
>>> Francesco Fragomeni via Alt-photo-process-list
>>> Sent: Monday, January 08, 2018 8:45 PM
>>> To: The alternative photographic processes mailing list
>>> Subject: [Alt-photo] Gum pigment mixed in batches
>>> 
>>> Hi all,
>>> 
>>> Quick question. I'm sure this has been asked but I can't find it. Can gum
>>> bichromate pigment be premixed in larger batches rather than being mixed at
>>> coating time? I'd like to mix stock pigment solutions and keep them stored
>>> in glass bottles that I can reach for across printing sessions (rather than
>>> mixing fresh for each print). Is there any reason not to do this? I think
>>> I've heard of people doing this but wanted to double check. Thanks!
>>> 
>>> -Francesco
>>> 
>>> _______________________________________________
>>> Alt-photo-process-list | altphotolist.org
>>> 
>>> 
>>> 
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