Color Printing before the Digital Era

Posted On February 06, 2018 | 14:25 pm | by jamesc | Permalink
James N. Carder (February 2018)

Four Photoengraved Copper Plates. Dumbarton Oaks Archives (AR.OB.Misc.092.a-d).

Color printing before the digital era was a labor-intensive and expensive process. For that reason, most Dumbarton Oaks publications that were printed before the late twentieth century had few color images. Before digital photography, color images for publications or postcards required the use of a four-color, photoengraved-plate printing process. The Dumbarton Oaks Archives has four copper-on-zinc plates (AR.OB.Misc.092.a-d) that were used in the 1960s to print postcards of a gold and cloisonné enamel reliquary in the Byzantine Collection (BZ.1953.20). Each plate measures 4½ x 3¼ inches.

Postcard Image of Demetrios Reliquary (BZ.1953.20), Enlarged Detail.

To make the four plates used to print the postcard, the object was photographed four times using color filters on the camera to record select color hues in the object: yellow, magenta (blue-red), cyan (blue-green), and black. The resulting four negatives were then screened (converted to tiny dots or halftones), transferred (“offset”) onto the copper plates that were coated with a light-sensitive medium, and etched with acid. In the printing process, each plate was inked with the appropriate corresponding color–yellow, magenta, cyan, and black–and the plates were printed in register; i.e., they were superimposed so that identical portions of the image in each plate overprinted one another. The result was the printed color image of the object.

Demetrios Reliquary (BZ.1953.20), Digital Image, 2011.

With the advent of digital photography, photoengraved plates were no longer needed. Inkjet or laser printers transferred the color-coded digits of the image to paper, a process that was both quick and efficient and considerably more accurate in color than the four-plate process.