GMDE has brought to the Press Center of Corriere della Sera in Pessano con Bornago it's trainees for a different job training from the usual... to discover the prepress and printing phases of newspapers.
From the editorial site to the printing plant
The first step of the newspaper production flow starts with the editorial site that transmits, through dedicated networks or ftp sites, the layout made using the editorial system (Gn4 Woodwing) to different printing sites.
Corriere della Sera uses tabloid format, arrangement of two pages on the printer’s sheet , (for example, page 1 and page 48, page 2 and page 47 for a pubblication plan of 48 pages). The tabloid layout allows fast plate mounting times, an excellent color register but requires high production peaks to manage the reception of files.
The standard format used for the distribution of the pages is the pdf, this document must be converted, by means of software called rip (Raster Image Processor), in the four color separations (cmyk). Color separations are bitmap images (tiffg4), file type compatible with the console (newsdrive) that converts the bitmap into a system of commands to be sent to the ctp for the imaging of the plates, made by the switching on and off of the laser, point by point through a modulator type AOM (Acousto-Optic Modulator).
The forming of plates
The plates used in the printing center of Pessano con Bornago are made of photosensitive polymers that exposed to visible light, UV radiation or IR radiation (for thermal plates) emitted by the ctp ,generate a chemical reaction by printing in the plate the graphism and countergraphism lipophilic and liporepellent respectively.
The plates are extremely sensitive to light sources, such as the phone torch, this requires strict protocols for loading these, such as the use of dedicated rooms with yellow safe light to avoid contamination.
Once the plate has been imaged by the CTP, it enters the processor, through a drive system (rollers and brushes), it goes through the "oven" section and then into the "gum/drying" section:
· The oven: increases the temperature of the plate up to 150 degrees, to fix the chemical reaction, hardening the graphism thus avoiding the wear of the same in contact with the blanket.
· The gum/dryer units: polymer residues not hit by the laser are cleaned away by the action of gum and brushes; a thin veil of gum finalizes the plate improving the ink acceptance properties and also gives protection from external agents (humidity, weather changes, scratches)
After the processor, the plates are punched and then bent by electronic/pneumatic system (NELA), the purpose of which is to create a sealing system on the cylinder of the press; an automatic system, via barcode reader, sorts and stackes on dedicated baskets the plates according
with publication/edition names.
The Offset printing
RCS printing plan uses Offset printing (AGFA N95 lowchem), a technology that ensures high run length and consistent high image quality. Offset printing produces sharp and clean images and type more easily because the rubber blanket conforms to the texture of the printing surface (thanks to the principle of repulsion) .It is an indirect print composed basically of three rotating cylinders: a plate cylinder, to which the metal plate is fastened; a blanket cylinder covered by a sheet of rubber; and an impression cylinder that presses the paper into contact with the blanket cylinder. Offset printing, as a development of lithography is based on the principle that water and grease do not mix, so that a greasy ink can be deposited on grease-treated printing areas of the plate(graphism), while nonprinting areas, which hold water, reject the ink.
The visit focused more on the pre-press department, then we had the opportunity to attend the departure and printing of an insert of the Corriere della Sera and the shipping processes with the involvement of the companies in charge for delivering the product at the collection points located on the territory.