Re: gum/dichromate ratios

On Thu, 10 Nov 2005, Dave Rose wrote:

> Rather than mix chunks of gum with water, why not use a gum arabic solution?
> It's readily available from any well stocked dealer that carries printing
> supplies. A one gallon jug will last for many years of gum printing.
>
> Dave in Wyoming
>
>
>> 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 :)
>> Kate
>>
>> -----Original Message-----
>> From: Christina Z. Anderson [mailto:zphoto@montana.net]
>> Sent: Friday, 11 November 2005 3:19 a.m.
>> To: alt-photo-process-l@sask.usask.ca
>> 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
>> diginegs.
>> Chris
>>> 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
>
>
>
Received on Fri Nov 11 13:32:46 2005