NuArc Platemaker conversion and exposing plates

For greater coverage I am posting on PPletterpress and Briar Press Discussions.

UPDATE: Platemaking experience with a NuArc FT18 platemaker.

Ok, so here is a recap and an update. I removed the glass top on the vacuum and replaced it with KREEN by creating a frame to hold it in and using the original hardware that was used with the glass plate. Until my 12 step gauge comes in I have a 14 step gauge that I tried to use but it really is no help

TEST 1: (6 - 3” x 3” pieces of polymer were exposed)
I started out with a unit of 17 which was about 00:01:45 for the test and run that up to a 79 unit exposure that was about 00:04:30. The longer exposure time increased the hardness of the plate but there was absolutely no shoulder to the artwork. I doubled the time for hardening. Commas and thin lines are weak but at the 79 units the plate is getting almost hard enough. At 99 units (approx 6 minutes) the letter forms bleed to a bold but shoulder thickness is still at a 90 degree angle to the artwork surface.

TEST 2: (6 - 3” x 3” pieces of polymer were exposed)
I purchased a DRAFTING FILM from the local art store. It has a frosted look but it is a smooth piece of plastic like material. I first taped it to the outside of the frame with a 1” gap between the FILM and the KREEN. With a 12 minute exposure there was very little hardening of the plate. Some letter forms even washed out during the first 3 minutes of hand washing the plate. Next I placed it between the KREEN and the NEGATIVE in the vacuum frame. I set the exposure to 99 and did another test. There is a very slight shoulder now and the hardness is getting better but it still is a bit soft even after the washout and hardening in the platemaker for 10 minutes without the film. The problems from test 1 are still there with the commas and thin ruled lines.

TEST 3: (6 - 3” x 3” pieces of polymer were exposed)
I added a second film for testing to see if it increased the shoulder angle. I did a timed exposure because the units stop at 99 and that is roughly 00:06:00 to 00:06:30 minutes on the bulbs current life cycle. I times an 8 minute, 10 minute and 12 minute exposure. The 12 minute exposure produced acceptable art without having the fonts grow to a bold weight. The shoulder however did not increase from the test 2 results with the increased addition of the extra sheet of film.

I even added tinfoil to the interior of the exposure unit in an attempt to reflect more of the light into the plate and broaden the shoulders but with no success. All it effected was the sensor for the interpolated (automatic) timer in which it turned it off quite soon after it was started due to increased light readings picked up.

I am at this point very open to more suggestions on ways to increase the shoulder width. Please let me know if anyone has heard of ways around this with and offset platemaker or if you know of someone I can talk to who has successfully converted one I would love to talk to them! I know that a Photopolymer platemaker has as bank of bulbs I however do not have the extra coin to purchase one. All I need is enough shoulder on the thin parts to do runs of 250 quantity with a reasonable impression in the paper.

cody

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