The line block technique, refined in the 1870’s is a hybrid of intaglio and relief printing. It begins with a negative of a line drawing being contact printed onto a photosensitized metal plate. Light hardens this emulsion into an acid resist while non-exposed areas are washed away in warm water. When etched in a bath of acid the metal surrounding the emulsion protected lines is eaten away forming a low relief. The plate is then rolled with ink, which will only adhere to its surface but not in the incised lines as with traditional intaglio, and then it is printed in the same manner as a woodblock. As the line block method can only print a single tone all values are created optically and a wide variety of textures were often added to enhance it. Since these plates are inked in the same fashion as relief prints they were usually adhered to blocks of wood to raise their height so they could be used in conjunction with letterpress. It was through their use in letterpress that these illustrations became known as line blocks. A great many trade cards and postcards would use line blocks in their production through the 1950’s.
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