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Mixing technologies sometimes doesn’t work
April 25, 2008
In my last blog I wrote about printing with wood type and a hand-cranked 1890 cylinder press. The next day we printed the second color. We had three people running the press: a crank operator (this is the most fun), a feeder, and a slip-sheeter, who inserted a sheet of 24 x 36 vellum between the printed sheets. With the kind of letterpress printing we were doing, the slip-sheet is very important. We put down a lot of ink, and the sheets set-off badly unless you protect them with a slip-sheet. When you run the second color, you have to de-collate the sheets first, then you do it again.
Three Cal Poly students operate the 1890 Campbell press: (l to r) slip-sheeter Val Sison, feeder (and museum Curator) Carol Pan, and cranky Daniel Lloyd at the hand crank. In this image you can see we have the ink vibrator and form rollers in place. Wash-up is not much fun.
The second color on the poster we were printing was a nice crimson red, which was used to print the two line illustrations on the poster. Normally I send these out for zinc or copper engravings, but this time I decided to try something new. Upstairs (in another century) we have an Esko Spark, the state-of-the-art tehcnology for exposing photopolymer plates for flexo printing. The Spark exposes extraordinarily accurate Cyrel plates with a carbon coating. The benefits are that you don’t make or use film, there are no problems with vacuum quality or speed, and the exposure is more consistent. I decided to try Cyrel plates and use them on the 1890 Campbell press in the museum, and my colleague Malcolm Keif did the honors on the Esko machne.
The originals were drawn in Illustrator, the plates were exposed and processed for routine flexographic printing, and then I mounted them on blocks of “high base” – in this case made of exotic Brazilian Cherry. We used normal, soft photopolymer to make the plates. I was careful to use a micrometer to measure the base, the adhesive and the plates so that it all came out “type-high” – .918 in.
On the press, though, the soft polymer was distorted by the rotating cylinder, causing the designs to print badly. I reduced the tympan pressure by cutting away the tympan sheets, and reduced my impression to a minimum. But, the result was slightly less than acceptable to me. The client, our university Library, was still thrilled with the result (it looked antique!).
I’m not sure if it’s even possible to print with a big letterpress machine and soft plates. Next time I will go for zinc, I think. The experiment was a success – I learned that fancy-schmancy spark-deposition plates and 19th century printing equipment don’t mix.
But we had fun.
Posted by Brian Lawler on April 25, 2008 | Comments (0)
