RE: gum/dichromate ratios

From: Kate M ^lt;>
Date: 11/10/05-03:16:31 PM Z
Message-id: <000301c5e63c$063f86e0$d535f6d2@kateiwpiarptn6>

I have to agree with Chris here - the amm.di.needs to be at about 15% for
digital negs. I found this out by a lot of experimentation......
I also mix my gum "as needed" rather than keeping a bottle full, that way if
I can't get back to printing for a while, I'm not throwing old gum out, or
using toxic preservatives. I'm very aware that I'm exposing myself to toxic
chemistry all the time, even with the precautions I take. You might say I'm
paranoid about it :)

-----Original Message-----
From: Christina Z. Anderson []
Sent: Friday, 11 November 2005 3:19 a.m.
Subject: Re: gum/dichromate ratios

I use I part gum powder to either 1 or 2 parts water, weight to volume, and
then use my gum/pigmnet to dichromate as 1:1, but the dichromate part of the

equation is either 1/2 water 1/2 saturated dichromate or 3/4 water 1/4
saturated dichromate. In other words, I only use a 15% or 7.5% dichromate
solution in my mix.

Lately i switched to the 15% as I'm testing my new curves and colorized negs

and such, just because the layer is very stable and if I want to let it
automatically develop (e.g. sit face down in water) the color falls off just

fine, or if I want to spray develop it holds up to spray perfectly. But I
don't use saturated dichromate 1:1 any more since switching to
>I use 1 part of saturated dichromate to 2 or 3 parts of gum/pigment
>mixture. My gum is commercial 14 baume. Less toxic and expensive chemicals

>(ammonium dichromate) the better. As you can see the ratios are flexible
>and you will do best finding your own workflow.
> Marek M
> Houston

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Received on Thu Nov 10 16:06:19 2005

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