...[Tenniel's] method for creating the illustrations of the Alice books was the same as the method he used for Punch, namely preliminary pencil drawings, further drawings in ‘ink and Chinese white’ to simulate the wood engraver’s line, then transference to the wood-block by the use of tracing paper. Then the drawings were engraved to the highest standards.... In 1981, the original wood-blocks were discovered in a bank vault where they had been deposited by the publisher. They are now at the British Library. Tenniel’s original drawings remained black and white for over 40 years until 1911, when eight prints in each book were hand colored. (http://www.alice-in-wonderland.net/resources/background/tenniel-and-his-illustrations/)