[Alt-photo] gum 'solarisation' issue

Joseph Smigiel smieglitz at gmail.com
Sun Jul 30 22:32:47 UTC 2017


John,

That has happened to me in the past as well. I believe it is staining related to particular pigments. In my case it was Bone Black. I've uploaded a pic showing some tests done with a Stouffer tablet:

http://smieglitz.tumblr.com/image/163613468740

Look familiar?

Joe


On Jul 30, 2017, at 1:27 PM, John Brewer via Alt-photo-process-list 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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