Hobbies And Interests
It All Began...
"Printing" is a misnomer, measured by today's methods of computerized imaging. It all began with wooden blocks, hewn by hand; the earliest known book that used woodcuts came about in the mid-15th century. By the mid-16th century to the late 1700s, almost all books were illustrated from copper plates. During the early 1800s, Louis Daguerre and his partner, Joseph Niepce, created the first photographic process and the first metal engravings by photography. Later that same century, use of a "screen" by William Talbot in England, creates dot patterns--still in use today--known as half-tones. By 1883 commercial half-tone screens were in full swing in the U.S., and all but replaced woodcuts in the printing process. Half-tone color printing followed about ten years later, and it is still one of the most common color printing processes. Later the photography process lent itself well to lithography--known as photo-lithography--which, unlike earlier engraving or photogravure processes, permits printing over large, solid areas. Finally, advent of the offset printing method added speed and flexibility, and replaced "lithography", although the term applies to both processes.
The Photo Process
The primary difference between "Photo", or photogravure, and "Litho", or lithography, in philatelic printing--as in other media--is in the process, not the finished product. The differences between the printed stamps are barely noticeable, except under extreme magnification. The above image is an example of a "Photo" printing (Scott Catalog,’, Israel). Without the color, all that would remain would be black dots that illustrate the photo-plate impressions. A photograph of the design filters through a screen and transfers to a metal plate. The process breaks the transfer into minuscule dots that, after a chemical wash, form depressions in the plate. After ink is applied to the plate, then wiped away, ink only remains in the depressions. Those inked depressions form the original design when applied to paper. Therein is the primary difference between the two processes.
The Litho Process
During the lithography process, paper never touches the plate, but rather, in modern process, the image transfers from the plate to a rubber sheet, or a rubber-covered cylinder, and transfers again to paper. This method, known as offset printing, results from using an oily formula, followed by an acid wash to wick away ink from areas not covered by the oily substance. The end-product is a flatter, but sharper image. The radio-and-telephone stamp (Scott Catalog,ú, Israel), above, is an example.
Similar, But Not the Same
The difference between the two stamps is barely discernible, if at all, to the naked eye. In fact, numerous images exist in philatelic catalogs where stamp-issuing authorities have redrawn and reissued the same designs years later under the combined listings of, "Photo and Litho." Each process comprises several different methods which produce the same result. A stamp-issuer's sophistication, the modernity of its printing facilities and the design result the issuer wants to achieve, are factors that determine which process is used. Nevertheless, to a stamp collector, the process rarely makes a difference--except as a means to identify different issues of the same design and denomination.
Color Outside the Lines
Note that both of the above images are basically black-on-background; multi-color stamps commonly employ the photogravure methods. That process provides greater flexibility to manipulate a variety of colors and shades, using black with only the primary colors of red, yellow and blue.