There are two main points to consider when looking at an illustration. Who created the illustration, and what artistic method did they use to create it?
The work of an illustrator can have great impact on a book’s value and desirability, and demand from collectors. The true first edition is generally the most sought but artwork by a prominent illustrator can make even a much later edition very valuable. Some good examples would be the 1935 reprint of James Joyce’s Ulysses with illustrations by Henri Matisse or Salvador Dali’s take on Shakespeare’s As You Like It from 1948.
If basing your collection around a specific illustrator, it is wise to invest in a good bibliography or multiple bibliographies, and become familiar with online resources like Worldcat.org, or the websites for the Library of Congress and the British Library.
There is a vast array of famous book illustrators that attract collectors. Arthur Rackham, Edmund Dulac, N.C. Wyeth and Walter Crane are just a few famous names known to book collectors.
You can tell a lot about a book from the way that the illustrations were created. Some collectors fall in love with the way a certain medium looks and will purposely seek out this type of illustration.
Hand drawn images are uncommon in books simply because of the time it takes to replicate each page. Hand drawn sketches, watercolors, paintings and calligraphy are nearly always reserved to limited editions and specialty art books and accompanying inscriptions.
Woodcuts are a form of relief painting (something which is embossed from the real surface of painting) where images carved with the grain into soft wood blocks with knives and chisels create a raised picture that can be inked over and pressed onto paper thus transferring the image. These are the earliest forms of printed illustrations that began in Europe around the end of the 14th century and the 8th century (or possibly earlier) in East Asia. Wood block printing was also the technique used to create blockbooks.
This process is a similar concept to the woodcut except that rather than using a soft wood and cutting with the grain of the wood the artist uses a hard wood and cuts against the grain. The harder wood makes the process more difficult but allows for a greater degree of detail in the final print. Wood engraving was pioneered in the late 18th century and continues to be used today.
This is a form of counter-relief printing where the surface to be inked is lower than the areas to remain blank. After the entire surface of the plate is inked, the higher surfaces are wiped clean and the paper is forced into the groves to receive the ink. Early types of intaglio printing (1500s) were prepared on copper plates and these eventually gave way to more sturdy metals such as steel as new technology became available and print runs increased requiring a more durable plate. Types of printing in the intaglio family include aquatint, mezzotint, and engraving.
An etching artist uses acid to make marks on a metal printing plate. They apply an acid resistant coating to a plate and then mark lines with a needle where the acid will be allowed contact with the metal. Depressions are created where the acid has touched the metal creating wells for the ink to collect in. With aquatint the artist will repeatedly dip the plate into the acid mixture each time applying an acid resistant substance to areas that have achieved the desired tonality. The result is an etching of multiple depths that has a watery look varying in tone.
The first tonal method to be used, this is achieved by roughening the plate with small dots made with a metal tool called a rocker. These tiny pits in the plate hold the ink when the face is wiped clean. The result is a varying tonality in the print.
With engraving, the design is simply cut into a metal plate using a burin (that’s a chisel to you and me).
Invented in 1796 by the Bavarian author Alois Senefelder, lithography works on the chemical principle that grease and water repel each other. There is no carving in lithography and all design is done on the surface of the stone or metal plate. To create the image, an artist draws on their plate with greasy substances in the design they wish to apply and then covers the plate with a water film. Ink is then applied to the plate where it will only stick to the greasy design and be repelled by the water. Thus when the paper is pressed onto the stone a mirror image of the artist’s design is left in ink on the paper.
Stemming from the process of lithography, chromolithography was developed in the early 1800s as an easier way to make multi-color prints. In the simplest terms, chromolithography is a colored image printed by many applications of the lithography technique - each new plate being used for a different color.