Judy Seigel (jseigel@panix.com)
Fri, 15 Jan 1999 03:24:17 -0500 (EST)
On Thu, 14 Jan 1999, Cor Breukel wrote:
>
> Warning: this will become a long, winding post!
The best kind.
> ... I had also the
> sensation of a particular shade of orange, a memory of the streets in a
> Guatemalan town (Antigua) I visited. So I decided this was a good excuse
> to have a go at Gum printing. I knew on forehand that this technique was
> time-consuming, and time it took, lots of it..;-)..
Obviously it will get faster with experience, but how many masterpieces do
you need?
> lith film, I didn't find it that easy to identify the emulsion side).
All the lith film I'm familiar with, the emulsion side is distinctly
lighter. You just flip back & forth while looking at it sideways in the
safelight -- that is, you quickly look from one side to the other. The
emulsion side is unmistakable seen this way...
> method the direct positive procedure as described by Liam Lawless in the
> second issue of The World Journal of Post-Factory Photography.
> I used my JOBO CPE2 for the processing steps up to the clearing bath. I
> must say that this was extremely easy and convenient, no need to touch or
> move the film.
> After the first negative the tank obviously is wet; I prewetted the second
> negative to be able to slide the film into the tank. It will take some
> practice to judge the first exposure as well as the flash exposure
> correctly. I decided on a base exposure of 18 sec. (normal exposure of 6
> seconds) and tested several flash exposures: 10%, 15%, 20% and 30% of the
> base exposure time.These negatives showed quite different densities: the
> 10% flash was obviously the most dense one; the 30% was very flat; even
> the difference between 15% and 20% was considerable. I guess this is in
> line with the observations as reported by Judy and Sandy. So the flash
> time is extremely important. The (deepest) shadow parts seemed to have the
Liam has worked out a method using a univac (well, no, just a calculator
with an exponentiometer) to calculate the flash for a given target density
exactly. It will be in next issue, for those who can understand it. (I
sort of understand it already, almost, tho I don't have the dingy, & I
thought when I tried the process it was easier to find the flash by one
test strip than to do math. But for those who can, the method is awesome.)
> THE PAPER
> THE PRINTING
> I used the 10% negative for the first Cyanotype print. I used classic
> chemistry and a short exposure in order to only print the fence and the
> gate. This was easy. Next came the gum coat. I settled for Burnt Sienna,
> and after a few stepwedge experiments I used 1 ml gum + 1,2 g. Burnt
> Sienna + 2.0 ml saturated Potassium Dichromate. The coating went avarage I
> guess, I definitely need more practice. Another nasty property of the
> paper became apparent: it buckled; so registering was difficult.
That sounds like an extraordinary amount of paint for that amount of
emulsion. What brand was it? Didn't it flake?
As for paper buckling, on page 15, issue #1, Basic Gum, is an artist's
rendering of too -thin paper that buckled. I don't see which paper you
finally used, but for anything larger than 8x10 I've given up my flighty
ways and stick with heavier (more dimensionally stable) paper. For 8x10
however, I'm enjoying an unpretentious little Somerset book. It's cheap,
stronger than you'd think in such a light weight, & a lively surface. But
ng for larger.
If you do use a light paper, 2 hints: Coat & smooth quickly before the
paper has time to buckle. There's a brief grace period. Also, trim the
paper so most of the sheet will be wet. A large uncoated border around a
wet interior accentuates buckle. If the paper is buckled when it's dry, do
what someone just said (I think, maybe I dreamed it?). Between sheets of
heavy glass with a gallon of water on it for 20 minutes or so before
registering.
> I settled on to gum coats with the 15% negative. I cleared for 30 minutes
> up to 1,5 hours. (Does a shorter exposure and subsequent short clearing
> equal a longer exposure and longer soak?)
Probably not, but there are too many equations to be sure for all.
Generally, the longer soak opens up more shadow steps. If it doesn't wash
away highlights at the same time (which it may or not depending on
strength of the emulsion), equation won't be the same. But this is verrrry
tricky to foretell, because sometimes paint washes off the whole business,
lightening the color. And sometimes not.
> A obvious conclusion is that I am not there yet..;-)..the possibilities
> are infinite with Gum it seems, as well as the time needed for it...
Sounds like a bravura beginning, cor. Very impressive. Congratulations.
Judy
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