From: Christina Z. Anderson (zphoto@montana.net)
Date: 08/17/03-09:35:04 AM Z
YEA!! Another gum printer! Yes, you do have enough to get started, but
you'll need more colors in the long run.
Loris, is your gum powdered or in lumps? If powdered, mix it up in COLD
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.
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.
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 cream,
and use that in drops added to the gum before you add the gum to the
sensitizer. To figure out the amount, brush on a scrap of paper to see if
the color looks right. For an 8x10 gum, for instance, I use 1/4 tsp gum and
1/4 tsp sensitizer, in your terms that would be about 1 ml gum and 1 ml
sensitizer, and add your drops of color to that. I have petri dishes I use,
and a glass rod, so I mix in that and use a hake brush which fits well in
the petri dish.
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
notorious for fading so make sure yours is lightfast, otherwise I would
switch to some other magenta color.
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.
Mix your potassium dichromate up in a 10% solution. Or, dump and pour: get
an amber glass jar and fill with distilled water and put your dichromate in
that, making sure that there is always sediment on the bottom to assure the
top liquid is always a saturated solution. Don't shake upon time of use,
and take your sensitizer off the top. This lasts forever.
Upon time of use mix gum and color with the pot di 1:1 and add your bit of
color.
Chris
----- Original Message -----
From: "Loris Medici" <lorism@tnn.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, August 17, 2003 8:09 AM
Subject: How to prepare gum arabic solution?
> I purchased "dry" gum arabic ("tears"?) and want to prepare gum arabic
> solution. Can you please help me about the method/formula?
>
> I have potassium dichromate (dry - powder) the following (half pan form)
> watercolors: sepia, alizarin crimson and gamboge (all windsor newton
cotman
> series). Is this "arsenal of raw materials" ;) enough for starting gum
> bichromate? What is the method to mix half pan watercolors with gum arabic
> solution?
>
> Regards,
> Loris.
>
>
>
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