In the plate printing process, ink is applied to a plate so that it remains only in the engraved areas. Paper is then laid atop the plate, and the two are pressed together under great pressure. As a result, the ink from the recessed areas is pulled onto paper, creating a finished image. Plate printing is used for the portraits, vignettes, scrollwork, numerals, and lettering that is unique to each denomination.
The engraved plates are mounted on the press then covered with ink. A wiper removes the excess ink from the surface of the plate, leaving ink in the recessed image area of the plate. Paper is applied directly to the plate and under tremendous pressure (approximately 20,000 lbs. per sq. inch), the paper is forced into the engraved plate, thereby removing the ink and printing the image.
Sheets that are printed from the back plate printing process require 72 hours to dry and cure before they move to the face plate printing process. As the sheets dry, they bond and stick together. Therefore, the sheets must be separated and neatly jogged before they can be printed on the face press. The load is turned on its side and, through the combination of vibration and forced air, the sheets are separated. The process takes approximately 10 minutes. Once jogged, the load is moved to the designated face press.
While the same printing process applies to the faces as the backs, one difference is how the ink is applied to the engraving. Special cut-out ink rollers transfer the different inks to a specific portion of the engraving, thus allowing three distinct colors to be printed on the face of the note; the black for the border, portrait engraving, and signatures of the Secretary of the Treasury, and the Treasurer of the United States; the color-shifting ink in the lower right hand corner for the $10 denominations and higher; and the metallic ink for the freedom icons on redesigned $10, $20, and $50 bills or color shifting ink on the redesigned $100 notes' freedom icons. Bills printed in Fort Worth, Texas, will also have a small "FW" printed in black ink. The loads of these freshly printed sheets will still require 72 hours to dry and cure before they can continue to the next operation.
The next operation is dependent upon whether 32-subject notes are being produced versus 50-subject notes.
For 32-subject sheet production, the next steps are currency inspection, COPE (Currency Overprinting Processing Equipment) , and note packaging.
In 50-subject sheet production, the next step is LEPE (Large Examining Printing Equipment).