You asked:
>I have access to a few pound containers of Gum Arabic Powder and
>Crystals. It's very inexpensive. I believe it's used in lithiography. My
>question is, should I be concearned about the quality?Could it be much
>different from say what I get from Photographic Formulary? How long will
>it last? And finally, Is the crystal or powder better for Gum Printing?
If it is the white powder it is fine. Put say 100 g in a container and add 100
ml of cold water and leave it until it dissolves and use that. Do not mix it all
at once as the liquid, without preservatives does not last as long. The colour
of the brown powder works through to the print especially in subtle colours and
gradations.
As to the 'crystals' treat them in the same way but strain the liquid through
muslin to remove acacia twigs and camel dung.
As to preservatives, I usually only make a small amount so that I do not need
them. Some books suggest using mercuric chloride to kill off the bugs but it is
quite good at killling off people as well. Others suggest formaldehyde which is
also noxious.
The current fashion on the list is glyoxal as a hardener for gelatine rather
than formadehyde but i am not sure whether it acts as a preservative as well.
I have beside my keyboard a bottle of a preservative used in the cosmetics
industry Euxyl K 400 which is relatively easy to get hold of . Does anyone on
the list have any experience of this substance ? It may be all right for gum
prints as it is formulated to put on faces. Its active ingredient is
1,2-dibromo-2,4-dicyanobutane at 0.05 % to 0.2 % concentration. In its
undiluted state the material should not come into contact with the skin or the
eyes ( but then etchers happily dabble in 10 % nitric acid ). The bottle has an
interesting logo with the letters ' S & M'.
Terry King