At C.S. Graphics, Singapore, a pressman checks a sheet from Hong Kong As It Was.
Offset printing, in essence simple, in its details is extremely complex, demanding and always exciting.
In offset printing the printing plates separate a book’s photographs and texts into ‘colours’ (for example, for duotone ‘grey-scale’ images black and some shade or tone of grey; or for ‘full colour’ cyan, magenta, yellow and black). As each plate spins on a press cylinder, it is constantly inked for impressions showing one integral ‘colour’ of the book’s photographs or text. The different ‘colour’ plates then roll their inked impressions onto the ‘offset’ cylinder. This prints directly onto the paper, as the sheets move through press.
Press checking, as seen here, aims to ensure that the final printed sheets exactly replicate, or perhaps slightly improve on, the book’s wet proofs. Press checking is intense and demanding – and exciting! The decisions made here, with machine time (and so costs) always a factor, critically affect a book’s final appearance. The pressmen and publisher compare the proofs with the test printing sheets for fine details – of image contrast, density and sharpness. The latter is closely related to ‘registration’, whether the different ‘colour’ plates are set up on the press precisely in line, in two dimensions, given a tolerance of minute fractions of a millimetre.
Press checking is the ultimate fine tuning: to the amounts of inking, each ‘colour’ of ink, nudging the plates on the cylinders to improve the registration, and other inter-related factors. Various trade-offs are sometimes a stressful aspect of press checking: gain more shadow detail here, then we lessen the highlight detail there. Quick comments and judgements flash to and fro between the pressmen and publisher: ‘I’d make the change but what do you think? Overall – gain or lose?’ Once each sheet’s reproductions are perfect, or as close to perfect as technically and visually possible, the printing begins.
Then the book’s sheets race through, at about three to four sheets per second, with occasional stops to check the inking and clean the press cylinders. A pungent glorious smell, printers’ ink, permeates the space. Sheet by sheet, the final and long envisioned book appears. Pallet load by pallet load, the sheets are trundled away for the subsequent production work. This takes some weeks: drying the sheets, then folding, cutting and binding them.