From: Loris Medici (lorism@tnn.net)
Date: 08/17/03-02:39:12 PM Z
Hi Christina, thanks for the answer.
----- Original Message -----
From: "Christina Z. Anderson" <zphoto@montana.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, August 17, 2003 6:35 PM
Subject: Re: How to prepare gum arabic solution?
> Loris, is your gum powdered or in lumps? If powdered, mix it up in COLD
It is in lumps.
> water in a 1+2 or 1+3 solution--nowadays the usual is 1+3. One gum
printer
> mixes dry powdered gum up at time of use, but I like having the bottle on
> hand. You HAVE to add a preservative or it'll sour on you and stink
within
> a short week enough to be unpleasant to work with. Preservatives are
> formaldehyde, methylparaben, sodium benzoate, thymol, and others I am
sure.
> Tell us what preservative you have on hand and then I'll dig out the
amount.
I have "formalin" (37% solution of formaldehyde) - I had purchased it for
keeping mold away of my Cyanotype A solution (ferric ammonium citrate). What
is the correct amnt. of formalin?
> Benzoate (my use) is .25% of your mix. This lasts years.
>
> I used my gum right away (15 min) after mixing and it was fine. It will
> clear in 24 hours and not be so white/foamy, but it still works
immediately,
> contrary to many books. Of course, I mixed mine up in a food processor.
> Others use a dedicated whipper, like a hand mixer thing.
>
> If you have tears, you have to soak them much longer--a day or two. Always
> cold water (hot changes the gum). They used to suspend the tears in
muslin
> in their water but that is not necessary--just soak, unless you see lots
of
> impurities, and in that case, suspend them in a muslin bag. Nowadays our
> gum is much purer.
So you say that the lumps will dissolve in water if soaked a day or two?
Interesting... I think I'm going to crush the lumps in a mortar in order to
convert them in powder and then mix it with water + preservative.
> You have to mix your half pan colors into a "cream" and then use that in
> your gum/dichromate mix. I have never used anything but tube and powder
> pigment, but that shouldn't be hard to do. Just mix a heavily colored
Actually powder pigments were my first option but I only managed to find
iron-oxide pigments (many, many colors) and the seller told me that these
pigments are insoluble in gum arabic solution. So, should the pigments
definitely dissolve in gum arabic solution or also a suspension will work?
> ...
> It seems you have a Y, R, and a brown. Try a monochrome gum at first, but
> you'll need a blue, and a black is always nice. Alizarin crimson is
Yes I will start with mono - that's why I got the "sepia". I will use
cyanotype as the blue layer (gum over cyanotype).
> notorious for fading so make sure yours is lightfast, otherwise I would
> switch to some other magenta color.
For instance?
> When you get addicted to gum, I would suggest you get some good tube
> pigments. Ask the list and they can give you brand names that are readily
> available in your area--Winsor Newton are great, but some are very
> expensive. I use Daniel Smith and M. Graham and WN, but not the Cotman
> ones, which I think are the cheaper form.
Unfortunately I couldn't manage to find any tube pigments (other than
acrylic and oil) in my area.
> ...
Thank you very much for the valuable information.
Regards,
Loris.
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