researchers: Dan Dawson and Hannah Hurricane Sanchez
May 25, 2019
Room Temperature: 69° F
Since we had decided last week to reinvest time in developing a film positive that yields better tonal ranges and clarity, we also thought to re-explore our aquatint screen exposure time. This is a tip we had gathered from an email exchange Dan had about ImagOn HD film with Susan Groce from the Department of Art at the University of Maine, her recommendation was to find an exposure time for the aquatint screen that was the longest possible before a tonal wash out in the print.
Our first test was to design a step test exposure time for the aquatint screen. We had been exposing the aquatint screen at 5LU and achieving a rich black, we wanted to see what a step test from 20 LU to 45 LU (using 5LU intervals) would yield. After exposure, we placed the PETG plate into a developer bath at 68.6°F for 9 minutes, rinsed the plate with running water, spayed with white vinegar and rubbed for 30 seconds, rinsing again in water and patting dry. We then printed the plate using Aqua Ink’s Carbon Black ink with about 15% transparent base. The Hanemeuhle copperplate paper soaked for about 20 minutes, was blotted and printed on the Charles Brand press with a pressure of .9/0.
Our print showed little to no variation between exposure time, and the print showed solid black.
Since we had not seen any break down in tone in our first test print, our next test we pushed the aquatint exposure time even more. The second step test that exposed the aquatint screen to 25 LU, 50 LU, 75 LU, and 100 LU. After exposure, we placed the PETG plate into a developer bath at 68.6°F for 9 minutes, rinsed the plate with running water, then sprayed with white vinegar and rubbed for 30 seconds, rinsing again in water and patting dry. We then printed the plate using Aqua Ink’s Carbon Black with about 15% transparent base. The Hanemeuhle copper plate paper soaked for about 20 minutes, was blotted and printed on the Charles Brand press with a pressure of .9/0.
The results of that print showed good blacks in the 25 LU and 50 LU areas and showed a tonal loss in the 75 LU and 100 LU areas. Because the blacks were a little stronger in the 25LU area over the 50LU area we decided to proceed with an aquatint exposure time at 30 LU.
Now, we needed to expose, develop, and print an image to test this new aquatint screen exposure time. Using an ImagOn laminated copper plate we exposed the aquatint screen to 30 LU. Using the film positive printed with a 45 curve that we created last week we exposed the plate and film positive to a 7.8 LU exposure time. Another recommendation we had received from Susan Groce was to perform a flash exposure, we decided to give this technique a shot. So after the initial 7.8 LU exposure, we set up a .2 LU flash exposure. The 9-minute developer bath was 72°F, after developing the plate was rinsed with cool water, sprayed with white vinegar for 30 seconds, lightly rubbing. Then rinsed again with running water, and patted dry.
To test the effectiveness of the additional flash exposure, we processed another plate using the same method as above, just without the .2 LU flash exposure.
Both plates were exposed to 200 LU as a final hardening exposure after developing.
Printing the plates was the same as before. Using Hanemeuhle Copperplate paper soaking for about 20 minutes and blotting dry. Using Akua Carbon Black with about 15% transparent base, and the pressure stayed at .9/0. Wiping with a tarlatan and a final wipe with the phonebook paper.
The printed results showed a surprising difference with the .2 LU flash exposure and no flash exposure. Without the flash exposure, there is loss of middle tonal grays, and much more heavy darks and an overall loss os subtle tones. These results lead us to adopt a flash exposure as an important part of the film positive exposure process. Still not happy with the printed results we felt the 7.8 LU with .2 LU flash exposure had still little to no light tonal grays. The following week we plan to shorten the initial exposure time.