U of S | Mailing List Archive | alt-photo-process-l | Re: more and more and more solarplate

Re: more and more and more solarplate

Christina Z. Anderson wrote:
Keith and Jon,
Have you ever run a step wedge group side by side of different ratios of exposure times within your parameters to see how the tonal range is affected up and down the step wedge? For instance, if you do a 44/44 sec exposure, to do a step wedge at 10/78, 20/68, etc. etc...
No, I haven't. That approach sounds pretty comprehensive though. What I have done is apply that principle to doing a step grid using gradient circles to give me a ball park, then use a step wedge against those times to find the curve adjustments. http://www.terrabear.com/procedures/polymer_photogravure.html#test

In the test above I'm using colored inks, but the first test when trying to nail exposure times should be using black ink only, ideally with little or no modifiers. Once you have solid black as you can get, and a good blend of tones, you can modify as needed using ink combos as well as the curve.

The reason I ask is that I find it odd that Diane Longely just gives the aquatint that 1 minute after the image exposure. Although she does say to vary this ratio to achieve the correct tonality of the image. But it seems as if she is giving a minimal exposure just to deal with open bite.
This makes sense to me. That's really all the aquatint is supposed to do - give tooth so the whites don't wash out entirely leaving open bite. Too much exposure to the aquatint and you burn out highlights, however. Too little and the plate gets to be sticky and mucky in the shadows.

I got some good points out of her book to be sure. One was the fact of plate tone within the varying plates--solarplate having lots of plate tone and others having none.
Not so. I just opened a fresh 20 pack of KM73s (yummy). I tried to keep them as out of ambient light as much as possible this time as I was troubleshooting some other issues. Unlike my last batch which I was pretty casual with, I tried to keep these in the dark as much as possible. The result: quite a bit of plate tone. Too much in fact. I read in Dan Welden's book this can be mitigated by flashing the plate after screen/image exposures with sunlight for 1-5 seconds. Could be that since this batch was so fresh, and the fact that KM73s are more sensitive to light than solarplate I've just been introducing a little burnout to the highlights all this time through my sloppy workflow... Granted I have Box Car ship them to me direct from Vreeland, and I don't think they've been opened since leaving the factory in Japan. If you buy a small stack from box car, they've had to open a larger pack to sort and send them to you, and who knows if they do that in the darkroom or where...

BTW I got no mottling yesterday with an image wherein I powdered the positive and not the plate. But I'm SURE it is purely luck.
Cool. I still need to try that test. Powdering both plate and lightly dusting the positive still gave me patches. Why are you sure it's luck?

Have fun at the conference. Look for my friend Angela Faris. She teaches at the Colorado Arts Institute in Denver and is taking a hiatus from doing polymer plates to finish her next book, but is very much interested in this process as well.