There are five, maybe six, different methods of printing.
1. Relief printing, where a raised image is covered with ink and pressed against a bit of paper. Letterpress is the main occupant of this space, but it was preceded by woodblock printing (see The Diamond Sutra), and, even earlier, printing from seals. Originally used to impress an image into a yielding medium like clay (or sealing wax) seals were already by about 300BC being used by Chinese officials to stamp silk or paper documents with an inked “imprimatur”. Indeed the word for “to print” in Chinese, yin, originally meant “to authenticate a document with a seal”.
Linocuts, potato prints, and those old John Bull printing outfits, where little rubber letters are inserted into a holder and inked on an ink pad then stamped onto something your parents aren’t going to object to, are familiar relief printing methods for children. Those office date stampers make us all relief printers.
2. Intaglio printing. The opposite of relief printing: a recessed image rather than a raised one. An intaglio plate prints from an image incised into a metal plate, filled with ink, cleaned off, and then yielding up its ink to a sheet of paper pressed into it. Gravure, or Rotogravure, is the commercial application: it costs so much to prepare the image-bearing roller that the process is now used only for extremely long runs where great color fidelity is required, e.g. labels for cans of baked beans. On a more intimate scale, here’s a video showing dry point and etched prints being made. (Click on the title of this post if you can’t see the video here.)
While a signet ring doesn’t print intaglio when it is making its mark in that red wax blob on your envelope, it could. Imagine smearing the ring’s surface with Nutella®, polishing it carefully and pressing it firmly onto the envelope for a delicious impression.
3. Planographic printing. Neither raised nor recessed — the image sits on a flat plate, working by the magical incompatibility between oil (the greasy ink) and water. Commercially planographic printing effectively means offset lithography, but of course it started off as direct offset; discovered by the footloose, carefree (and smart) Alois Senefelder at the very end of the 18th century. Find a flat stone; draw a picture on it using a wax crayon, douse it in water, put ink on it (it will flee the wetted areas), and put a bit of paper on top, and Bob’s your uncle. The following video, from the same MoMA series as the one above, shows the process is actually a little harder than that.
Unsurprisingly commercial offset lithography is quite different but the principles, oil/water antipathy, remain the same. It took almost 150 years for it to knock letterpress off its perch. (You can see the whole series of seven videos on Printmaking at Khan Academy.)
4. Ink jet printing. Not a raised image; not a recessed image; not a flat surface with an image: no image, except for the digitized information about an image carried in a computer which directs the printer to squirt or not squirt. More and more commercial and Book Printing is going this way. This short video shows how it works inside your home ink-jet printer.
Although it’s not fundamentally different in terms of my surface analysis, being a sort of analog analogy of the digital-driven ink jet system, I include electrostatic printing as a fifth variety.
5. Electrostatic printing. Think office copier. You expose the image onto a selenium-coated rotating belt using a bright light (light, which can be regarded as a fast form of electricity, is able via a photoconductor to create static electricity on the belt); the belt rotates the charged image to a drum with toner powder; static electricity causes toner to stick to the bits which form the image; and the belt moves on to meet up with a sheet of paper which has been given its own electrical charge, which makes the toner jump from belt to paper; the image is fused via a pair of heated rollers; and out pops the still warm copy.
It was the adaptation of this process to book work (and the clever dodge of getting binding done by library-repair binders, who are used to binding single copies), which gave birth to the print-on-demand business. The original workhorse here was the Xerox DocuTech.
6. Recessed impression. The sixth method, the earliest, might not really count, as there’s no ink being transferred, but cuneiform characters incised into clay tablets have been found dating back to Sumerian times, about 8,000BC, and certainly played a role similar to that of printed documents. The technique could be used with positive or negative images: i.e. resulting in a raised image or a recessed image.
Of course, at a trivial level, I should probably note that we use the word “print” to distinguish a line of upper case letters from a cursive script hand. In the same spirit we might mention finger prints (relief printing), foot prints (recessed impression), photographic prints (planographic printing). We occasionally use the word to refer to an illustration, and to a design on cotton goods. Apparently a butter print is a lump of butter which has been shaped in a mould.
I’m not sure we can go any further: we’ve tried printing from a raised surface, a recessed surface, a flat surface, no surface, an indented surface. There’s nowhere else to go, up or down. Future developments will probably be tweaks improving on what we’ve already established.
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