Joseph Albert produced the first color collotypes with three collotype plates, each inked in a different color. In 1882, the Hoeschtype, which used six plates, was patented. Combination processes Mezzograph collotype Mezzograph was a trade name used by Valentine Co. Ltd. of Scotland, for their multicolored postcards, printed in a hybrid process where colors were printed via photolithography and then overprinted in black or blue collotype for the "outlines" of the image. Halftone collotype Halftone collotype processes combine halftone printing and collotype. These include the Jaffetype, developed in Vienna; the Aquatone, developed and patented by Robert John in the United States in 1922; the Gelatone process, introduced in 1939; and the Optak process, introduced in 1946. Characteristics Collotype was most often printed in monochrome in various colors of ink (black, brown, green, blue). In double-rolled collotype, the plate was first inked with stiff black ink and then re-inked with a softer colored ink; only one impression was taken. This process was most common in fancy postcards. Collotype has a finely reticulated pattern that captures the tonal shifts of photography with a much more subtle effect that other photographic printing processes of the late 19th century, such as halftone engraving. Under magnification, the edges of the print appear as diffuse fine curved lines, unlike the more defined edges of relief or intaglio prints. Richard Benson has described the finnicky nature of collotype printing, primarily problems of registration with damp paper and the varied tones from sheet to sheet. As a young printer during the 1960s, Benson recalled how superstitious the collotype printers were because of the delicacy of the process. Historical use The collotype printing process did not achieve commercial viability until Joseph Albert invented the first mechanized collotype press in 1868. Short runs can printed on a proofing press, but longer print runs are carried out on a flatbed machine, where the plate is made square, level and fixed on the bed. The plate is then dampened with a slightly acidic glycerine–water mixture which is selectively absorbed by the different gel hardnesses, blotted before inking with collotype ink using a leather nap or velvet rollers. Best results are achieved with hard finished paper such as Bristol, placed upon the plate and covered with a tympan before slight pressure is applied. The collotype process uses much less pressure than other types of printing, such as lithography, letterpress or intaglio. While it