Process for printing on corrugated paper board

Claim 1

A process for printing on corrugated paper board, the board comprising flat paper liners adhesively fixed to the crests of a corrugated paper medium, the process comprising positioning a sheet of the board horizontally continuously throughout the process, passing the sheet through a top printing rotary letter press printing press applying a hydrophobic or oil based printing ink to the sheet's top liner at a film ink thickness of from 1.5 pounds to 2.25 pounds per thousand square feet of the printed area with a printing pressure below that crushing the sheet and forming wet printing ink impressions on the top liner, passing the sheet with the ink impressions still wet through a varnishing equipment applying a hydrophilic or water based varnish covering the wet ink impressions at a film thickness of from 1.5 to 2.25 pounds per thousand square feet of coated area and forming a wet varnish coating on the top liner, and passing the sheet with the ink and the varnish coating still wet under an infrared heater radiating heat uniformly to the varnish coating while forcibly holding the sheet flat against warping, and drying or setting the varnish.