Re: gum mixes

[Keith Gerling <keith.gerling@gmail.com>]

Hi Chris,

Since your keeping count, I'll chime in late, although I'm not sure
this will do much good.  I fill an olive jar a third full of Kordofan
powder (the bottle says Kordofan Gum Arabic, but in smaller print says
Acacia Senegal, so go figure...),  put in another third of water and
shake it up.  The next day I dump in more gum, shake more and just
keep adding gum until the frothy head stays at about a cm and the jar
is over half full. (Next time maybe I'll weigh it all out).  Preserve
with thymol.  At emulsion time I use one part of this "pretty
saturated" gum solution to one part of saturated Potassium Dichromate
along with whatever amount of dry pigment is appropriate and coat this
onto substrate that have I've misted thoroughly with a spray bottle
and brush - so the emulsion gets diluted at the coating stage.  Seems
to work.  I promise that by the time I write MY book, I'll reduce this
to something a tad more easier to follow.

Keith

On Jan 3, 2008 8:23 AM, Christina Z. Anderson <zphoto@montana.net> wrote:
> Dear all,
> So this is what I have so far--only 10 gum printers on the list apparently
> :)
> The range of practice of gum never ceases to amaze me. In historical times
> it was 10% gum to 100% gum (the latter was mixed 1 gum powder to 1 water--I
> know, it is not technically a 100% solution but that was what they termed it
> in those days--in other words, a 40% solution was 40g gum PLUS 100ml water,
> not in a total combined volume of 100ml.
> Some questions:  Marek, do you use dry am di at time of use?  Henry and
> David, at time of use you mix essentially a half strength potassium
> dichromate and am I correct with your 1 di: 1 water: 10 (!) gum?  How long
> are your exposures and are they in the sun? Guido, same thing--do you use
> that little potassium dichromate in your mix--essentially 1-5 parts gum to
> only 1/2 part pot di? If I have anyone's info wrong, let me know.
> Chris
>   1.. Sam Wang 1+2 powdered and at time of use 1:1 with dry am di
>   2.. John Brewer 3+10 powdered, preserved with 15ml formalin per liter, at
> time of use 1:1 mix, changing this ratio for highlights and shadows
>   3.. Kees Brandenburg 3+10 LUMP which he says is 14 baume and at time of
> use 1:1
>   4.. Marek Matusz premixed gum, stock pigment mixes of 1 tube pigment in
> 120ml gum and  at time of use 3pt gum/pigment to 3 pt water to 1 part AMT
>   5.. Joe Smigiel is premixed 14 baume and at time of use 1:1 pot di, tube
> pigments, sometimes powder pigments, sometimes mica or interference pigments
>   6.. Bill Mull is premixed gum and stock pigment made with gouache at 6
> gum: 1 gouache and at time of use 1:1 pot di and one coat gums made with
> paper negs
>   7.. Hamish  premixed gum and stock pigment solutions and at time of use
> 1:1, but sometimes 1:2
>   8.. Henry Rattle 70 to 200 Kordofan No. 1 LUMPS with few drops formalin
> and at time of use 1 di: 1 water: 10 gum
>   9.. Guido Ceuppens 200g to 850 water with 5gr sodium benzoate with stock
> pigments of 1 g watercolor tube: 6ml gum and at time of use 1 part stock:0-4
> parts gum:0.5 pot di
>   10.. David Hatton 500g + 1 liter with 10 drops 100% thymol and at time of
> use 1 pot di:1 water:10ml gum with varying amounts of pigment depending on
> layer, color
>
> ________________
> Christina Z. Anderson
> Assistant Professor
> Photo Option Coordinator
> Montana State University
> Box 173350
> Bozeman, MT  59717
> 406.994.6219
> CZAphotography.com
>
>
>