Have you ever wondered how exactly a modern book is printed? Well, below is a series of photographs showing some of what goes on when a book is on the printing press.
In August I travelled to Hong Kong at the invitation of the Asia Society to oversee the printing of their exhibition catalogue Picturing Asia: Double Take: The Photography of Brian Brake and Steve McCurry.
Te Papa was a partner with the Asia Society Hong Kong Center in mounting an exhibition of the same name (see my previous blog), and my job in particular was to see that the print reproduction met Te Papa’s standards, especially in relation to the work of Brian Brake that was illustrated.
The book was printed on a four-colour offset press. You can see here just how big it is.
There is an operator at each end and they have an audio system to talk to each other because they are so far apart and the machine is so noisy. The upright panels contain the mechanism for printing each of the four colour inks: cyan, magenta, yellow and black. This consists of a series of cylinders and rollers through which the paper passes.
A book is composed of signatures, large sheets of paper that are cut and folded to make up bound sections of the book. On a machine like this, these sheets are printed one side at a time.
At the start of a press run, 50 or more sheets are run off to get the ink flowing nicely and everything settled in and then the printer whips a sheet out to check how things are looking.
Here’s the back-end, where the assistant works and where the paper is fed in, with each sheet lifted off the pile by suction hoses.
Here’s the bit I was involved in, the checking of printed pages against proof prints previously prepared to make sure the colour and density (lightness/darkness) matches. The printer also carefully examined registration marks on the corners of the page to confirm that each of the four colour plates that are printed to the sheet are precisely superimposed.
If the colour or density need adjusting, then the printer uses the digital slider controls you can see across the front of the desk here. These are a bit like the level controls in a recording studio and with them you can increase or decrease any given ink at any strip across the sheet.
Where it always gets tricky is when one image follows another in the direction the sheet goes through the press. If you add more magenta to one image then this will also happen in the other.
A particularly difficult issue arises with printing images that run across the centre of a page spread. The two halves of the image might be printed in two separate sheets and only come together when the section is assembled and bound. It is very easy for the colour on one sheet to print slightly different on the other.
And when it becomes a real headache is if you want to adjust another image before or after (in terms of direction of travel of the sheet through the press) an image half. Then you will need to make the same adjustment on the other sheet (which, hopefully, you haven’t already printed). This in turn might affect a third image on that sheet.
You can see here that one image, printed in half in two separate parts of the same sheet (see previous image), is cut and joined up to ensure the colour and density matches at the join where they will later be bound together.
The printing plates are thin metal sheets, one for each colour ink. They are wrapped around a cylinder. This is a stack of the used ones.
The printing plate doesn’t actually come in contact with the paper being fed with the machine in the offset process. Instead, the inked image on the plate is transferred to a rubber blanket that then prints onto the paper. This means that the plate doesn’t wear, so long print runs are possible. And the slight sponginess in the rubber enables better contact with the paper, so greater sharpness is possible.
Each time a sheet is printed the four plates need to be removed and the new ones added in. Here is the printer’s assistant holding the old plate as it is fed out. The new plate is at top and is ready to be slotted in and around its cylinder.
When the plates are changed the printing blanket is wiped down with powerful solvent to remove any trace of the old image.
In total, it is a time-consuming business changing over four plates, cleaning the blanket, and running test sheets and checking the quality. But once everything is set it is only a matter of five or so minutes for a sheet on a book like this to be printed.
Here’s a stack of finished sheets, each consisting of six pages on one side. They will need to go through the press again for printing on the other side. Then the sheets are set aside while the ink cures before they can be trimmed, cut, folded and bound into a book.
This signature will be cut to three leaves, each folded in half and slipped inside the other and sewn through the fold. What look like opposing pages of a spread on the sheet here will no longer be so when bound. Note the yellow image centre left and the upside down one above it.
Here they are as they end up in the bound book, now opposite each other and both the right way up. The complicated business of deciding which page is printed where on a sheet is known as creating the impositions. Software makes it easy to do these days.
Being Hong Kong, a workplace shrine makes sure the relevant deities are kept happy and good luck prevails within the factory.