From: Judy Seigel (jseigel@panix.com)
Date: 04/16/03-11:00:17 AM Z
On Wed, 16 Apr 2003, Christina Z. Anderson wrote:
> I found Demachy mixed gum/water in a ratio of 30-35%. Hence I took my
> powdered gum arabic from Daniel Smith and did this ratio, in my food
> processor. After reading hither and thither that it isn't good to use the
> powdered form, takes 4 or 5 days to settle, etc etc. I found that it whips
> up really well in the food processor, and after about an hour (?) or at
> least while I was measuring pigment powder, it cleared into exactly the same
> gum I buy in liquid form from D. Smith. Light amber, viscous, you name it,
> and half the price as the liquid form. In fact, I would bet D. Smith uses
> powdered arabic and mixes it themselves.
If you're getting a "light amber" gum from D. Smith, you may be buying
their "premium" gum, not their "lithographer's gum," which in any event
varies from year to year, and, being quite dark is almost certainly not
made by them from powder.
I gather their product line and pricing have changed. It's possible they
only sell one gum now -- but when I last bought a gallon of Daniel Smith
"lithographer's gum" for $16 it was quite dark--- and WONDERFUL. In fact
I suspect that something in the dark is good --it certainly worked much
better than the lighter "premium" I bought from them at the same time for
four or five times the price.
My favorite gum of all -- and it makes an ENORMOUS difference in quality
of clearing and other attributes -- is the RBP, which is now the Philben
house gum (and for those who care about such things, one used long ago by
Livick).
However any of those prepared gums has a preservative, which the gum you
mixed up presumably doesn't. There has been some claim that when the gum
goes sour it doesn't work -- that seems not to be true. In fact some
printers have said they PREFER the sour gum. However it does continually
change, lacking preservative -- so it would tend to work quite differently
over time. That is, your ratios/color effects, etc, would most likely
change.
There's also the matter of odor.... which some claim can get quite
intense as the gum sours.
Judy
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