METROPOSTCARD.COM Photo-Chromolithography



The development of the photochromie process in 1875 marked the beginning of reproducing photography in chromolithography without the use of halftones. The more commercially viable photochrom process was invented in 1886 and postcards began being produced through it at the turn of the 20th century. Many separate printing substrates would still need to be created for each tone of the same color as in traditional chromolithography for there continued to be minimal use of optical blending. This process begins with litho-stones coated with a photosensitive bitumen emulsion, which are then all exposed to the same photo negative through contact printing. The emulsion hardens in proportion to its exposure to light, and the unhardened areas are then washed away. At this point the retoucher removes all parts of the image not relevant to the color assigned to that stone while adding in needed texture and details. Each stone then goes through a very complicated etching process where most of the technique’s secrets lay. This manipulation of processing variables determined the nature of how and where the ink grain printed, which controlled the postcards final look. The stones were then printed in the same manner as a normal chromolithograph. At least six separate stones were required for this process though the employment of ten to fifteen hues was more typical to create a single image. The resulting picture, though completely broken down into small granules could still capture a fair amount of detail with a great clarity of color; but since they were based on black & white photographs the handling of color by retouchers could render the same image realistic or highly mannered. Only a few firms had access to this technology and it was practiced with many variables into the 1920’s.

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