Re: Gum Question -- Just Curious Mostly

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From: Katharine Thayer (kthayer@pacifier.com)
Date: 07/04/03-06:34:20 AM Z


Sally Makeham wrote:
>
> G'Day Y'All!!
>
> Coming out from lurking & learning long enough to ask a semi-
> hypothetical question about gum printing...
>
> Has anyone ever used any other type of gum (such as xanthan,
> guar,agar-agar, etc) besides Gum Arabic for gum prints??? Has
> anyone ever experimented to see what the effects were/are, etc. Is
> there something special about gum arabic over the other types?
>
> Unless there was some property of the other types of gums
> preventing their use, it would seem to my NON-scientific mind that
> as long as the viscosity was the same, then it could open up some
> interesting possibilities. ;o)
>
> I really would like to know this. If no one knows, then I MAY start
> to experiment a little. (After all -- someone had to be the FIRST to
> use digital negs, etc. LOL!)
>

Hi Sally,
This is an interesting question, and one I don't think has been given
much attention, so experiment away; we'll be interested to hear what you
find.

 A couple of thoughts:

I can't give a source for this, but I seem to remember reading somewhere
once that the lithographers' gum which many folks use and believe to be
identical to gum arabic is technically not gum arabic but some other
kind of gum, so it may be that not even everyone who thinks they are
using gum arabic are, although the difference between lithographers' gum
and gum arabic is probably less than the difference between gum arabic
and PVA or glue, which have also been used in "gum" printing.

I have a correspondent on this list whose observations about gum
printing variables have consistently differed widely from my own; it
finally turned out that when he prints in "gum" he actually uses gelatin
rather than gum arabic. After this revelation, I tried gum printing with
gelatin just to see for myself, but I wouldn't recommend it. For one
thing the low gel point of gelatin is a nuisance; it's necessary to keep
the emulsion heated to keep it from gelling while you're brushing it.
But more important, I found that the hardened gelatin image was
significantly softer than the hardened gum image, meaning details don't
stay crisp.
Katharine Thayer


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