Richard Sullivan (richsul@earthlink.net)
Thu, 25 Mar 1999 10:11:54 -0700
As long as we are on the topic of Ziatype coating let me put in my cent a
half's worth. First off, you have to see Carl's prints to believe them. He
gets, despite his protests, some of the silkiest smooth skies I have ever
seen done in platinum or palladium.
I recently worked with Martin Axon to see if there was a way to make
Ziatypes on Platine. The early concensus was that you could not.
The old proverb says there are many ways to skin a cat. True. I don't say
this is the only way to coat Platine for Ziatype but it is the one I have
found.
The trick is simple: Coat wet and brush brush brush. Brush way past the
point where you would normally stop. The paper is almost matte dull when
you quit. A good sable or artificial sable brush is preferred, but a good
Hake works fine. I use a rod to spread the solution around and then brush
it in from there. When you are finished rod spreading it there should be
about 1.5 inches of puddle left along the rod for an 8x10.
My theory on what's happening:
The Ziatype is a pop process and as such it "self masks." Thus the depth of
the image forming layer is less than that of a developing out image. This
may in fact be why you can get such incredibly smooth skies and tones.
Though I know of no tests that have been done, the Ziatype also appears to
have a higher resolving power. This makes sense if you accept the fact that
the Ziatype image is thinner. A thicker developing out image would have
less apparent resolution than a thinner Ziatype image if you take into
account the transparency of the surface of the paper.
The downside of the thinner image is that it must be >>in<< the paper and
not >>on<< it. Assume for a second that the paper is a series of hills and
valleys. If there are little puddles of emulsion in the valleys and it
dries, only the surface gets exposed and darkens. When it is washed, the
exposed tops of the puddles will wash off. When that happens you get
mottling and unevenness in the tone. Thus the Ziatype is more susceptible
to what I call tonal wash-off.
Carl's rod coating drives the emulsion >>into<< the paper. The force at the
curve of the rod is probably pretty high. The final pull-through also
removes any excess emulsion that might cause puddling in the valleys.
Platine does not respond to rod coating very well for the Ziatype. The
sizing is very heavy, tight, and thick. I think rod coating just slides the
emulsion around on top and never gets it down into the paper fibers. My
theory on the "wet brush brush" system is that since you use a lot of
coating, it eventually breaks through the sizing barrier. The continued
brushing keeps the puddles from forming in the valleys.
The coat "wet brush brush" system also works well with cranky papers and
poor printing conditions. My darkroom is 19' x 17' with a 12 foot ceiling.
We are in a metal industrial building with an un insulated roll-up door. In
the winter in Santa Fe it gets down into the tens and teens nightly.
Subsequently the building can get pretty cold overnight. (Were looking to
putting in a new door this year.) Cranking up the heat and humidity in the
darkroom is well neigh impossible at times, so I have been forced to work
in adverse conditions. I have found that the "wet brush brush" system works
well under these conditions.
Under cold dry conditions, a well behaved paper like Platinotype, which
coats with a rod very nicely, starts to behave like Platine. The sizing is
tight and slick and does not respond to rod coating very well. Thus you can
treat it like Platine.
Of course the rod coating method uses less emulsion, so from the B+S
perspective, it is not the best. On the other hand, if you are buying the
metal and not selling it, rod coating is the better on the pocketbook.
--Dick Sullivan
At 07:23 AM 3/25/99 -0500, you wrote:
>Carl, Salto:
>
>Your Ziatype problem sounds like a lack of practice with the physical
>process of coating. It *does* take practice to do it well, and the
>larger the print, the more difficult it is.
>
>For the paper you are using, first I recommend glass rod coating, rather
>than a brush. Second, use just enough coating, not a skimpy or overly
>generous amount. How much can only be learned by trial and error. Third,
>store the paper dry (50% rh or below) and humidify (a cool mist
>humidifier works well) just before coating. If you store and coat your
>paper at 60% rh or higher, Arches Platine will be a better choice.
>Finally, the coated platinotype paper should be surface dried with cold
>forced air after coating, then printed. It will become blotchy or grainy
>if left to dry without forced air. Platine can be dried either way.
>
>The "sharpness" difference between point sources and diffuse light boxes
>is real but neither one is "better". The point of a platinum print can
>often be lost if we seach for the same qualities we want in a silver
>print (intense dmax, ultimate smooth surface resolution)--might as well
>just print in silver if those are the goals. I use the "soft" diffusion
>lightbox, but then I also prefer to print from negatives developed in
>pyro: their enhanced edge adjacency may be a factor that compensates for
>the lightsource in the final impression of visual acuity.
>
>Let me know if I can answer any other questions.---Carl
>
>Carl Weese
>co-author, The New Platinum Print
505-474-0890 FAX 505-474-2857
<http://www.bostick-sullivan.com>http://www.bostick-sullivan.com
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