This section aims to give you an overview of the printing process once you’re happy with your artwork, you’ve checked your proofs and you’ve created your printing plates. This is the press run, where all your sheets of specially chosen paper are sent through the printing press and given all the ink you need to produce a lovely book!
We have more information in our ‘Stock & Paper’ section regarding papers and cards. Here we just want to let you know about the various classifications, and how they apply to the printing presses. As we use offset, we have a far greater selection of papers when compared to digital. An offset printer can calibrate their machine to different paper thicknesses and types; a digital printer on the other hand has to make do with a lesser range, and often only chooses to use the same papers for many different jobs.
Parent Sheet Size
This links back to the Pagination section, but essentially the parent sheet is the large sheet on which all of your individual pages are printed. We tend to fit up to 32 pages on the largest sheets, but as your book gets bigger, the fewer pages we can fit on each parent sheet. This is one of the reasons why the price goes quite so high on larger books.
Paper weight tends to refer to the thickness of the paper, though of course some styles of paper are denser than others, so it is always best to check the ‘real’ thickness of the paper when calculating your spine. For full colour ink jobs a thicker paper is always recommended to prevent any show-through. The manufacturer of the paper often provides ‘opacity’ readings, explaining how much shadow may show through to the other side.
Sometimes the desired thickness of card or material is not available. In this instance, it is possible to ‘duplex’ or glue two bits of card together to double the thickness. This is also how other cover materials, such as our Vegan or Faux leathers, are attached to card for notebooks such as cahiers. Duplexing is a similar process to laminating.
Sometimes, especially when printing colour books, you will have the ‘card core’ referenced. The core is there to increase the opacity of your card, to prevent any transparency, and increase the card’s strength. It has been duplexed to your outside layers – which can be paper rather than card.
There are different qualities of card core, ranging from low to high; corells, grey, white, blue and black. If you were producing a board game, for example, a low quality card is fine as the board is not handled. If you were to produce a pack of good quality cards, on the other hand, you would look to choose a better quality stock.
You have different styles of paper coating that result in both a different texture and look. This coating is applied to the paper during the manufacturing process, and can drastically change the way in which your images/text look, as the coating affects the way the ink is absorbed into the paper.
The most common coatings are gloss, matt, silk and uncoated. Uncoated is as it sounds – without any coating applied. This results in a rougher paper ready for workbooks, and also comes with a lower cost.
Matte coating sits next to uncoated. It smooths the uncoated paper, without too much shine. It also protects the paper from smudge marks and dirt. Silk coating is one step up from matt, providing a light sheen and a smoother finish to the paper. Gloss applies to the coating with the most shine, perfect for photos and crisp imagery.
There are two main types of printing; offset and digital. Offset printing uses etched metal plates that apply ink onto a sheet of paper, whereas digital printing uses electrostatic rollers—called “drums”—to apply toner onto the paper. There is a greater level of control available for offset printing, which is our method of choice. See our dedicated ‘Printing Methods’ resource for more detail on these.
What comes after the paper? It’s now time for you to put ink to paper! We’ve discussed CMYK colours before, which are the most common and produce almost all colours available to the human eye. However, if you’ve got a particular Pantone that you need to hit, you can order this particular ink and apply it separately to the paper from the CMYK. This is termed a ‘spot’ colour.
On top of the printing press is the ‘ink fountain’, a reservoir full of the required ink for that job. This sits above the ‘cylinder’ that holds the printing plate, and another holding the rubber used to transfer to the paper.
To prevent areas of the paper that do not require getting any ink on them, a water-based solution is applied to the plate to repel ink. This reservoir is also found in the fountain.
As you know, we use offset printing. The term ‘offset’ refers to the transfer of ink from one medium to another. We’ve included an infographic that shows how this process works.
Both ink and the water solution are transferred from their respective fountains through rollers down onto your plate. The flexible metal plate is wrapped around the plate cylinder, which rotates as the roller provides an even coating across the design.
The rotating plate then transfers ink onto the offset cylinder, which has a rubber blanket wrapped around it. The ink is then transferred onto your paper (parent sheet) that is fed through from a hopper. It may or may not have other inks already on it from previous parts of the job.
Finally, the impression cylinder both maintains pressure on the paper to allows appropriate transfer of ink, and helps feed the paper through.
Once all the materials and printing plates have been prepared, each part of the press is cleaned from the previous use to make sure your parent sheet gets a clean setup and the alignment is not thrown off by dirt. This is often done with a built in washing program.
The printing plates are then installed and the press is calibrated by the technician using calibration software. Calibration is when the press is configured to the specific type of ink and paper it is using in order to reproduce the colours as accurately as possible. Levels, curves and other tools are adjusted to produce the desired colour density. Colour density refers to the amount of light that is reflected off the substrate and the ink, which of course affects how the final colour is perceived. Paper thickness and coating are also taken into account as they affect how the ink is absorbed, again impacting the final appearance.
Next, the press is run at a slow speed so the first sheets can be checked against the technician’s proof, and any necessary adjustments can be made. When the technician is happy, the press is run at full production speed.
Once the pagination has been printed to the parent sheet, we can check the sheet and its colours against a large digitally printed proof to check the correct Pantones have been used. This is also a good time to check sheets for any recurring blemishes that may have made it onto the sheets – such as dust on the rollers. The technician can also fold a spare sheet down to check all artwork is the correct way up and so on.