Although photochromes have been around since the late 19th century in the form of tricolor prints, their production began to change more dramatically in 1934 with the introduction of CYMK process colors. Further changes occurred in 1936 when Kodachrome, the first high quality, multi layered slide film was invented that could be used for commercial photomechanical reproduction. Problems with the dyes however would not be resolved until 1938. New process cameras now made color separations for offset litho-plates, taking four halftone negatives broken down into CMYK (cyan, magenta, yellow, black) colors. The different halftone screens were then rotated to create a rosette pattern enhancing the method’s subtractive color properties. The printed photochrome cards resemble color photographs even though made through halftone offset lithography. While changing technology allowed for the production of many transitional postcards since 1934, it was the Union Oil Company that was one of the first to publish modern photochromes in number and make the style popular. They became available as giveaway postcards at their service stations in 1939. But with gas rationing enacted during the Second World War, they soon had little need to advertise and the technique was not revived until after 1945. Mike Roberts was also an early pioneer in this medium who did much to make it popular. Some publishers thought this process a fad and continued to print linen cards. Up until 1939 almost all color postcards were manufactured by heavily retouching images taken from black and white photographs. But because no serious retouching was needed on these photochromes they became much cheeper to manufacture, and almost all postcards have been printed as photochromes since the mid 1950’s. The large variety of printing techniques that postcards were manufactured in had already vastly decreased, but the coming of the photochrome also marked the end of the artist’s hand on postcards. Though the process has basically remained the same since inception it has not been static as color quality has continually improved since the early dull grainy cards. As photochromes began to dominate the postcard industry much of the printing moved away from small publishers to large multi-national corporations who produced cards in ever larger numbers. In order to insure a long shelf life images tended to grow blander. At first photochromes were highly sought out by collectors because of their novelty, but as years past their sterile look led them to be considered almost worthless. Though these cards are still considered modern, many of the scenes that they portray are now over fifty years old and they may have changed more than some cards of a hundred years. This factor has now created a renewed interest in a select number of these cards among collectors. A number of modern photochromes originally referred to themselves as kodachromes. Others were more subtle stating they were taken from natural color photographs. They are now usually just called chromes for short.
Use the link below for a more compleate history of this period.