During the 19th century colorants was often added to printed images by hand for it was the most cost efficient way to produce a color image. This tradition was naturally applied to all types of postcards, and it became common practice around 1902. The general tendency of collotypes to print lightly while still capturing great detail made them the perfect receptor of hand coloring and they formed the base for most of this work. With more paper surface left exposed and a less oily ink to fight the water based colorant it could more easily show off subtle hues or attain brilliant saturation. Some publishers would even adjust the transparencies used to create collotype plates so that their cards to be colored would print lighter than the versions to be printed solely in black & white. Most postcards were colored with a simple RGB pallet but there are many variations to this. As labor costs rose the hand coloring of postcards faded out after the 1930’s.
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