[Alt-photo] gum 'solarisation' issue

Jack Brubaker jack at jackbrubaker.com
Mon Jul 31 01:34:35 UTC 2017

I've been visited several times by solarized gum. There's been speculation
about it here in the past. I've yet to see an explanation.

On Sun, Jul 30, 2017 at 1:27 PM, John Brewer via Alt-photo-process-list <
alt-photo-process-list at lists.altphotolist.org> wrote:

> Hi guys
> What could cause gum to solarise? It's happening in the light tones, all
> the dark tones are fine. Stouffer step 1 half on/half off substrate the
> same. Gradients are fine until step 10 and then it gets darker until step
> 21. Step 21 visually looks like between step 4 and 5
> I'm not doing anything different from the past; gum mixed by me 14 Baume,
> 13% pot dichromate, M Graham ivory black pigment, FAEW HP 300gsm paper,
> colorbyte substrate, UV source. As soon as paper is dry it's immediately
> exposed and then developed. I can't think I'm doing anything different than
> I have in the past. While I do have a new printer - Epson P600, it's not
> just that as it's happening on my Stouffer too.
> Stumped!
> John
> --
> John Brewer
> www.thevictorianphotographer.com
> www.johnbrewerphotography.com
> workshops:equipment sales:chemistry sales
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