A block book, as its name suggests — they tended to be rather short, so wouldn’t have appeared like blocks of paper — would be printed from a block, most often wood, but potentially metal, which was carved to leave the areas to be printed black (or more often dark brown) at surface level while the background would be recessed. The entire page, pictures and the text would be carved by hand. In the illustration below the white areas will all have been carved away to leave the outlines to print. (The red lettering was most likely added by hand after printing.) At my recent post on Tarot there’s a picture of a wood block used to print cards.

Block books, and block-printed anything —indulgences, playing cards, calendars, etc. — were the way you would duplicate materials prior to the rapid development of letterpress printing which followed from Gutenberg’s invention of movable metal types. As the examples of block books which have survived all date from after Gutenberg’s breakthrough, the “prior to” in the first sentence might appear redundant, but what’s true of books isn’t true of all printed materials. Actually we have very few survivals anyway, and the older a block book was the less likely we are to have it come down to us. Certainly block printing, which has been shown to exist in China before the 2nd century, has a long history though evidence for its arrival in Europe before the mid-fifteenth century is lacking.

Wood block printing certainly co-existed with early hot metal printing — no new technology immediately displaces its predecessors. After metal types became available it was not uncommon for the text of a “block book” to be printed on a press using metal type after the illustrations had first been printed from a wood block. Eventually of course metal type text and illustrations cut into wood blocks would be locked up together in a single forme and printed together in a single pass through the press.

Because the “impression” was usually applied manually, by rubbing or hammering the paper against the inked block, block books would only be printed on one side of the paper. If you turned the sheet over and rubbed it again, you’d smudge the ink! The blank sides were often glued together when the book was assembled.

The first printed image of a bloodletting man in Europe, which appeared in a calendar printed as a block book in 1474. Joannes Regiomontanus (1436-1476), Calendarium, Nuremberg 1474.

This is the earliest diagram we have giving instruction on bloodletting. It comes from a 66 page block book calendar printed in 1474. Link via The Collation, the Folger Library’s blog. Read the Collation post for an interesting discussion of the science of bloodletting. Most importantly apparently it was important “to avoid bloodletting when the moon was in the sign of the zodiac governing the part of the body to be bled.” The block book shown comes from the Library of Congress.

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A horse of a different color is the book block.