The preferred wood for blocks is boxwood, due to its incredible density and hardness. Blocks can withstand many thousands of impressions. Comparing the encyclopaedia illustrations with other earlier Chambers publications reveals that blocks used in the 1860s were initially made and printed up to 30 years before, for company publications such as Information for the People and Chambers's Miscellany of Useful and Entertaining Tracts.
One such is a tract on 'Wood-Engraving', first published in 1845 in Chambers's Miscellany, a version of which is included with the same illustrations alongside updated text in the encyclopaedia printed twenty later. It is included again in volume ten of the second edition in 1892. These encyclopaedia entries were edited and later expanded by J.R. Pairman, originally a wood engraver at the Chambers firm and by the 1880s, Head of the Art Department. The articles describe the changes in woodblock cutting and engraving techniques through the centuries. The second edition entry makes reference to the influence of photography in image styles evident when comparing the two editions.
The 1845 tract describes the process:
"During the last twenty years, it will have been observed how great has been the increase of works containing wood-engravings either for the purpose of illustration or embellishment. In the present sheet are several of this species of wood-cuts or engravings, and few publications of a cheap class are now issued without them… Wood-cuts possess a peculiar value, from the comparative ease with which they can be printed. While [metal] plate embellishments require to be produced by a process so tedious, that a man can with difficulty execute 250 impressions in a day, a wood-engraving can be printed with great rapidity by a machine to the extent of many thousands daily. The chief value of the wood-cut, however, consists in its being adapted for printing along with letterpress. It is inserted among the types by the compositor, and impressions come from it along with the letterpress which it is intended to illustrate. The reason why wood-engravings possess these qualities over metal plates is, because the figures or marks to be shown in print are left raised on the wood, the parts not to be printed cut away. This is the reverse of the principle of metal-plate engraving, in which the figures or marks are sunk, and hence the difficulty of effecting impressions with any degree of rapidity."
For the first edition of the encyclopaedia, the engraved woodblocks were made as part of an integrated printing system, as described in the quote above; that is the blocks were printed together with the metal type making up the text. The most time-consuming part of the process was ensuring the wooden blocks were exactly 'type high' in order to print a clear image. This could involve hours of pasting layers of paper, known as make-ready, onto the back of the blocks, to ensure a good quality print. The vast majority of the Chambers blocks show evidence of make-ready.
The process is described in the encyclopaedia's entry on 'Printing'.
"Before printing, however, a laborious process called making ready [their emphasis] has to be gone through. When many wood engravings are in the pages many days may be taken up making ready a single sheet. This process is for the purpose of making the impression equal all over and properly printing the wood engravings, and can be judged by comparing a carefully printed book with a daily newspaper, which is printed just as it comes without any making ready."
The woodblocks preserved in the Museum collections show that a different method of image reproduction was in use by the 1880s for printing the second edition. These blocks were also made from boxwood. While there is an image engraved on the block, where there is a background around the central image, this has not been removed by the engraver, as was the case for first edition blocks which were printed from directly.
These later blocks were engraved to be used as templates for the creation of stereotype or electrotype plates, some examples of which are also preserved in the collection. Both types of plates require a mould to be taken from the engraved block, from which a metal cast is produced, either made of type metal – a stereotype – or created by means of an electrolytic process – an electrotype – which creates a thin copper plate on the mould that was then removed and backfilled with type metal. Both techniques produced high-quality facsimiles of the original wood engraving. The same process was applied to the text entries, or indeed whole pages, reproducing text and image together in one plate.
The major advantage of these processes was the creation of multiple images (and text), allowing multiple printings on different presses. It also meant the original block could be retained as a template and reproduced on demand when the copies wore out. Copies could also be sold to other publishers.
According to archival records, the Chambers firm adopted a printing workflow with their American partners, J. B. Lippincott, that involved the Chambers firm sending entire stereotyped pages of the second edition of the encyclopaedia from Edinburgh to Philadelphia. The goal of this joint workflow process was that the encyclopaedia volumes would be released simultaneously in North America and in the UK, allowing both firms to claim copyright to the work in both countries, as there were no enforceable international copyright agreements in place at the time.
While the textual content came from contributors commissioned by W. & R. Chambers, some of the illustrations that appeared in the second edition, such as maps of American cities like San Francisco, were commissioned by J. B. Lippincott. However, it was the Edinburgh firm of cartographic publishers, J. Bartholomew, who created the maps which appeared in the printed pages of Chambers's Encyclopaedia.