410 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1951 



The halftone screen, hoAvever, did not achieve perfection overnight. 

 Like most mechanical devices it grew slowly from the original idea, 

 and a long series of trials and errors over a period of four decades 

 was necessary to bring it up the ladder to practical success. It is 

 with the more interesting of these efforts that this article is concerned. 



The letterpress industry, it should be remembered, produced prac- 

 tically all reading matter until recent years. Yet as late as the 

 1880's, despite the fact that photogravure and collotype (as well as 

 lithography to a less reliable degree) could reproduce photographs 

 beautifully by photomechanical means, the letterpress printer still 

 required the wood engraver to translate photographs and other toned 

 pictures into engraved blocks. Results were slow, costly, and unre- 

 liable. They were, moreover, marked by the stylistic idiosyncrasies 

 of the engraver. Here was letterpress, the most widely used method 

 of printing, producing all the newspapers, books, and magazines, yet 

 lacking any good method for producing toned pictures photomechan- 

 ically to set up in the same form with type. There was good reason 

 for inventors to work feverishly to satisfy the insistent demand 

 for a reliable photomechanical relief halftone process. Basing their 

 work on all that had gone before, they gradually evolved the modern 

 halftone screen, which was perfected in principle in 1885. By 1891 

 the difficult business of manufacturing accurate screens was finally 

 worked out. 



In the matter of creating graduated tones, relief printing lagged 

 considerably behind gravure from the historical standpoint. From 

 the fifteenth century up to the latter part of the eighteenth, the old- 

 fashioned woodcut provided the only means by which an illustration 

 could be printed in the same form with type. This was strictly a 

 line process, with only a rudimentary suggestion of tone. There 

 was the chiaroscuro woodcut, of course, which employed separate 

 blocks for tones, with a key block in line. This method, however, 

 required several printings and moreover had but a few simple 

 gradations of tone. Numerous methods existed in gravure, however, 

 for creating fine lines, dots, cross-hatches, and reticulations which 

 produced the illusion of tone. These processes, which included line- 

 engraving, etching, mezzotint, and aquatint, involved the engi'aving 

 or etching of sunken lines and dots which were filled with ink, after 

 which the surface was wiped clean and the plates were printed on a 

 special engravers' press which forced the dampened paper into the 

 sunken ink-holding lines and dots. No type could be used in these 

 processes. Consequently, when tonal pictures were required for book 

 purposes, the only solution was to tip in plates printed by gravure. 

 This was a costly and time-consuming procedure. 



In 1784 Thomas Bewick, in England, published his illustrations in 

 "Select Fables*' and demonstrated the practicality of creating tonal 



