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Re: curves for gum printing
-----Original Message-----
From: Keith Gerling
>Gum is the process with which I have the most familiarity.
I have had the
>most success using an Epson Photo EX printer, MIS inks
(black only),
>inexpensive Hewlett Packard paper (that I wax) and NO CURVE
WHATSOEVER.
It just goes to show (once again) we must each work out the
nitty gritty details according to our own goals and methods.
Unlike Keith, I have found I need to apply a rather radical
adjustment curve. There are so many variables that I
hesitate to even send Jacques Verschuren my curves (although
I will, off-list ). For one thing I have yet to completely
calibrate the proper color in which to print the negative to
match the density range of the gum emulsion (much like
calibrating development time in Zone system work). Another
factor is the medium onto which you print your negative, and
how you treat it (waxing, oiling, etc.). Probably the most
important factor is the type of gum used, the pigments, and
the type of paper support and sizing methods. The
possibilities expand exponentially.
I am using an Epson 1160 printer, using Epson photo quality
inkjet paper, Epson inks, and oiling the paper with mineral
oil. I am currently using only the black ink, although it
is a bit too dense if applied 100% (part of the need for the
radical curve). I found that the colors suggested in Dan
B's book were not dense enough. Need to do more testing.
Of course, this will change again when I switch from black
gum pigments to color. I'm also looking forward to trying
some samples of the Pictorico transparency material (thanks,
Larry).
Gum printing has flexibilities not available with other
processes. My attempts up until now have involved multiple
printing with the same negative and trying to adjust the
curve accordingly. I am fairly convinced that a better
approach would use different negatives for each successive
gum layer, or possibly multiple exposures through different
negatives on each layer (much as described in Dan's book).
The digital path we have embarked on is long, twisting, and
illuminated only by the faint glow of user's manuals. To
top it off the course of the path changes with each new
generation of hardware and software. Let's continue to help
each other find the way.
Garet Denise
Garet@Cornerstone-Inspection.com