The Dry Printing Revolutionby Franklin Noll on 07/27/20
A Four-Station Power Press, 1929
A revolution occurred in banknote printing in the mid-twentieth century. This was the transition from the wet method to the dry method of intaglio printing.
Until the mid-1900s, banknote printing involved the repeated moistening of sheets before each printing. The process was something like this: a sheet of secure paper would be wetted and then the banknote backs would be printed on the sheet. The sheet would then be allowed to dry (along with its inked impression). A few days later the sheet would be moistened again, and the banknote faces would be printed. The sheet would need to dry before any surface printing and numbering could occur.
Wet printing was necessary because of the presses used. Flatbed presses and later four-station power presses did not produce a great deal of pressure on the printing plates. So, the paper needed to be moistened to make it more pliable and more receptive to taking the image from the intaglio plate.
This wet method of printing was time consuming and laborious. It also limited the size of the sheet that could be printed—limiting the number of subjects (banknotes) that could be printed on each sheet and hence, productivity. The problem was that wetting and drying the sheets caused them to expand and shrink in unpredictable ways, leading to registration problems. In the US, the largest sheet that could be printed via the wet method would hold 18 notes.
A way was needed to print banknotes on dry paper. No wetting meant no shrinking or registration problems. And, the size of the sheet would only be limited by the intaglio press and the processing equipment downstream in the banknote production process. Two developments were needed to attain dry printing: more powerful presses and quick-drying, non-offsetting ink.
By the mid-1950s, new inks were available to allow dry printing. And, new, rotary intaglio presses were coming onto the market that exerted far greater forces than the old power presses. So, by the late 1950s, the dry-printing revolution had arrived. The rest is history.