On 19th May the SYP Oxford had a fantastic visit to Acorn Press. Acorn Press has been operating for over 35 years, and has a workforce of over 45 people. They participate in the FSC chain of custody, which ensures sustainable printing – helping the environment.
A few days before the visit, our fabulous Marketing guru Lea created and designed our own eight page, 4x4, booklet and sent a PDF of the artwork with a 4mm bleed and crop marks. The PDF proof was approved and we were ready to print. Our beautiful brochure (front cover below), was printed using offset lithography.
A proof is a close representation of what your final printed product will look like. It is not a colour check but a check to ensure that the content appears correctly without any corruption and that the pages are in the right order. Proofs are produced from the printer’s RIP (Raster Image Processor). This converts PDFs into a file that can be used by the plate setting software.
First we were taken down to the design studio and shown the proofreading table. Acorn Press is one of the only printers to offer a free proofreading service to ensure there are no pesky typos in your files.
Next our printing plates were created using computer-to-plate, an imaging technology. Typically books are printed in eight pages sections. A section or signature is a group of pages that are printed on both sides of a sheet of paper. This is then folded, cut and trimmed to the finished page size.
A printing plate is generally made of a thin flexible metal. The image from the RIP was transferred onto the printing plate using photomechanical processes. A plate for each colour was prepared. Our brochure was 4x4, meaning it was four colour on both sides of the paper in CMYK. That stands for the four inks used in colour printing – cyan, magenta, yellow and key (black). Looking at our printing plates through a magnifying glass we could see the dots of colour making up the image.
Printing plates are a vital part of offset litho printing. The plate is chemically treated so that only ink will stick to the image areas. Areas without image reject the ink. The metal printing plate is rolled around a cylinder in the printing press. Ink and water is applied. This cylinder rolls around and transfers the inked image to another rolling cylinder known as the offset cylinder covered by a rubber blanker. The paper is fed through between this cylinder and another cylinder called the impression cylinder. The pressure between the two cylinders transfers the ink to the paper.
Acorn Press has two presses, a KBA Rapida and a Heidelberg. The KBA is smaller, printing 13,000 sheets, double-sided, five colour or four colour plus sealer/varnish an hour. The Heidelberg is much larger, printing six colours at a time (this can include pantone colours) plus a coating, at up to 15,000 sheets an hour. This press is so heavy that the concrete floor in the printing hall had to be reinforced so the vibrations of the machine didn’t damage the floor.
In the cutting room, once all the sheets are printed, the stacks of paper were shaken by a machine to straighten up the edges and remove air between the pages. The stacks were taken to the guillotine where the white edges on the paper are cut off by a very sharp blade.
The printed sheets were folded together by a machine before being saddle-stitched. This is a common binding style used for booklets under a certain extent. It is often assumed the pages are stapled together, as it looks like two staples. The unbound pages of the booklet went across the saddle stitching machine – looking much like saddles on a horse. They were then literally stitched together with a very large, sharp needle and wire thread.
Once all stitched they booklets received their final trim to align the edges. The booklets were boxed up and generously given away to us.
Thanks Acorn for a great visit!