Re: Formulary Gum change

On Wed, 5 Nov 2003, John Cremati wrote:

> I wonder if the darkened gum has something to do with the various
> regions gum is harvested from, the time of year it is harvested, or
> possibly a variety of the gum tree species , or how much rain the area had
> that particular year... ... Maybe there is a processing technique involved
> as well that has a effect..

I was told that the dark color was caused by drought in the acacia fields,
tho of course that could be an old geezer's tale. However I have not
found any relation between darkness of of the gum and either the color or
the stain of the print. And tho I have found, as Katharine did, that the
gum is a very crucial variable in staining, I did dozens of tests (about
10 at once) of the same color and one variable changed at a time -- the
gum, the dichromate, the size, the paper & the time of hardening the size.

What I found was sort of mind boggling -- one change could suddenly send
the print off the chart in speed, or stain, or steps. For instance a gum
might "work" fine with one paper & not at all with another. Tho that combo
could be good with a different color. (I also found that time in the
hardener was a big variable.)

In any event I had been warned and warned others against using a
proprietary gum-- that is "nameless" from a 3rd party sold under the 3rd
party name. It's risky to calibrate around an anonymous gum whether from
Photographer's Formulary, Bostick & Sullivan or the US Treasury, because
as noted the company can suddenly switch sources & do so without prior
notice. Not that there's any guarantee even when you buy direct that
there won't be changes from lot to lot, but at least it's the same
manufacturer, likely to be using the same preservative & distilling
method.

Anyway, when I found a gum I liked, I bought two gallons of the same lot
number (at $17 per gallon) and having about 6 gallons to work out of, they
last for a long time (and don't seem to change with age, or if they do, so
slowly I don't notice).

> Has anyone tried any of the powdered gum sold thru Columbus Clay
> Company yet? They charge $5.30 a pound for powder, and they also sell
> solution at $17 per gallon..
> John Cremati

The trouble with powdered gum is you have to add a preservative, that is
if you don't want to mix fresh each time, which will have its own
variables. On the bright side it's likely to be quite light, if you care
about that.

PS: Last I heard the house gum at Philben was RBG (RBG?), a great gum that
used to be hard to get on your own.

Judy
Received on Thu Nov 6 00:10:32 2003