Re: dichromate stain

From: Christina Z. Anderson ^lt;>
Date: 06/15/04-07:51:11 PM Z
Message-id: <003701c45344$b2f70070$463dad42@oemcomputer>

Hey Tom,
    I'll throw in another theory (thinking about Judy's water theory):
today, reading thru the articles out of the BJP on gum, I came across one
from 1882 about a particular dichromate process: the writer nonchalantly
said that it was common knowledge " Calico printers that dichromate
thus altered by exposure to light forms a mordant...", meaning that it would
grab onto dyes in direct proportion to exposure, when the printed cloth was
immersed in a dye bath. Now, iron was one of the substances used in this
guy's photographic process that attached itself to bichromate. How about
iron content in our water? Of the three places I have gum printed, the only
one that has city water is SC, and it smells like bleach. Here in MN and
also in MT huge amounts of iron in the water--both well water. My prints
have been clearest in SC, but I just assumed that the more stain I've been
seeing here was due to working on unsized paper. I guess I could test it in
a dev bath of distilled water for my next print, since I have a gallon on
hand...never a dull moment in the gum world.

----- Original Message -----
From: "Tom Ferguson" <>
To: <>
Sent: Tuesday, June 15, 2004 8:05 PM
Subject: Re: dichromate stain

> OK, I'll add my data points to this confusion ;-)
> I use to get moderate dichromate stain. I now get almost none. I'm 99%
> sure it went away (many years ago) when I installed a fan in my
> light-box. I've always "assumed" that the ballasts in my UV tubes were
> generating enough heat to "mess with the system".
> I know I can keep coated paper for 6 hours without visible difference
> (dark hardening), I've never tried longer than that. I'm in Southern
> California, a moderate distance from the ocean. It is typically 35 to
> 40% humidity and 74 degree in my darkroom.
> OK, I have to go back to editing and photoshopping images of farm
> equipment...... I saw "Blowup" as a kid...... I just knew that
> photography would be an exciting and glamourous career :-(
> On Tuesday, June 15, 2004, at 04:16 PM, Keith Gerling wrote:
> > I've been too busy printing gum to read about printing gum, but for the
> > record:
> >
> > 1) Using halogen, fluorescent UV tubes, and a Violux plate burner, I've
> > never had dichromate stain. I've never seen it. In fact, I'm not
> > sure I
> > know what it looks like. (so maybe I do have it... nah - I've used
> > Sodium
> > Bisulphate on occasion. It does nothing.)
> >
> > 2) I've never experienced dark-hardening. Where I live in the
> > Midworst,
> > it's been extremely humid. I'm still developing prints I coated
> > yesterday -
> > no problem. They behave just like the prints I develop in the crispy
> > dry
> > winter.
> >
> > Keith
> >
> >
> >
> --------------
> Tom Ferguson
Received on Tue Jun 15 19:54:02 2004

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