I wanted to know more about color printing processes over the decades. That's me -- can't grasp the product without a peek at the process. I thought that the printing methods would have changed over the first 30 years of the 20th century. I thought if I put some common color postcards under a "microscope" (that is, scanned them at 2400 ppi), I'd see the eureka differences. Hmm...
The first few color views — from 1907 [Sample 1], 1913 [Sample 2], and 1924 [Smple 3] — look remarkably the same: a black and white halftone screen produced from a B&W photograph; then color added in splotchy patterns, probably applied with a "line block" prepared with a tint. (Click on the thumbnails below to blow up the patterns from different eras.
Click on thumbnails to enlarge:
The Linen Cards [Sample 4] look like the color was applied with mechanical color tints (dots of the same size in a regular pattern). By the modern photo offset era [Sample 5], true color halftones were being used (regular grid, but color dots of variable size).
[3.25.06] Two other color methods have come to my attention:
Sample 6 is an Albertype (a variety of collotype) that was hand-tinted.
Sample 7 is a collotype that was tinted with color blocks.
If anyone has additional helpful information or corrections, please let me know.
Coming up: dating photo postcards.
Updated 12.6.05, 5.1.13