If you look in the catalogues, you will find that most Irish stamps from 1922 into the 1960's were typographed. What is this process and why was it used so extensively?
Typography, also known as letterpress, is a process where the positive plate is inked on the surface, and the paper placed on top and rolled. The printing plate is positive, that is, the portion that will be printed is raised above the base of the plate. If you are old enough to remember manual typewriters, you will recall that the letters were made of raised metal on an arm. As a key was pressed, the arm raised and struck the ribbon that carried the ink. This, in turn, hit the paper, and, if adjusted correctly, caused the ink to be transferred from the ribbon to the paper only where the letter was raised.
In the case of stamps, the plate was cut away at those points where ink was not wanted. The high spots were inked from a roller, and the paper pressed to absorb the ink from the high spots. Plates could be made by cutting the metal or by etching it with acid. In summary, a fairly simple process. Figure 1)
What could go wrong? Debris, bugs, or dried ink can build up on the plate, eventually causing high spots to develop which would appear on the resulting stamp. A study by Pat Evans of the 1d penny red has over 40 different examples known repeating errors. (Figure 2 shows some notable error locations on an enlarged stamp). Paper wrinkles and folds happened, but were usually caught by quality control.
Typography usually limits stamps to a single color. Adding a second run through a different press causes problems with registration, and the ever-present problem of loading a page inverted.
Why use typography at all? Three major reasons - it is cheap, fast, and it is relatively easy to train operators. The press is relatively small and easy to work. Typography is often used to add overprints such as the 1922 Rialtas (Provisional) overprints and 1923 Saorstát (Free State) printings by Thom, Dollard, and Waterlow. The process worked well; problems from broken type arose when softer metal type in the Gaelic alphabet was used rather than hardened steel type. (Figures 3 & 4)
What were the disadvantages? The main disadvantage is in the handling of images. Certainly, images can be reproduced. Te conversion of a photo to a halftone is well known and works. Since it is a halftone, made up of small dots, definition is lost if the screen is too coarse. Newspapers are a good (bad) example. On a small item, such as a stamp, definition is worse. While this can be improved on using a halftone screen with more dots per inch, it then becomes more expensive.
Fundamentals of Philately, Williams, L.N., APS,
“Comprehensive Look at Key Stamp Subjects”, Repeta, L., American Philatelist, Vol.101,#2, February 1987, p128 ff.