To the author and editor, final files for books generally get handed off to a magician in the production department, and then the finished, printed books appear a few weeks later. But what happens in between? We’ve covered how books are bound, but what fairy dust is sprinkled to put words on pages?
There are three methods for printing that publishers can use: letterpress, offset, and digital.
Letterpress is the OG of printing methods. You can read more about literal typesetting here. A letterpress uses metal or plastic plates of type or images; the user rolls sheets of paper over the inked plates to transfer the image to the paper. It’s like super fancy stamping.
These days, letterpress is used for art, very limited edition books, and places where no power is needed. (See this post from Oh So Beautiful Paper for an inside look at artistic letterpress printing.)
After letterpress came offset. Offset printing began with “the accidental discovery that an image transferred to paper by a rubber covered cylinder was actually sharper than the image from the original type. This offset image gave rise to the name offset printing” (Self-Publisher’s 5-Minute Guide to Book Printing Processes). So, differing from letterpress, in which paper touches inked plates, offset printing has a rubber roller in between, so the ink goes from the plates, to the roller, and then to the paper. This gives the plates a longer life.
Offset printing allows way more pages to be printed at once, especially when using signatures (as mentioned in our bookbinding post). Offset can also do full-color books and has cutting and binding machines at the end of the printing process, like an assembly line that spits out whole books.
Digital printing is technology’s answer to offset. While with offset you have to print the number of books you think you’ll sell up front, with digital, you can print only the number of copies you’ve already sold. They are made-to-order and come out glued, trimmed, and with a color cover. Digital printers are essentially like super-fancy home printers. Also, you don’t have to work within the constraints of signatures, so you can have exactly the number of pages you need without blanks in the back.
Unfortunately, digital printing has yet to overtake offset when it comes to clean color images that are affordable. Thus, publishers today often use digital printing unless they have a book that needs color throughout or has an odd trim size.