Abstract: A leak preventing carton and blank for ice cream and the like in which the first-in and flap substantially closes the opening of the carton but leaves a gap along the top edge of the first-in flap which gap is prevented from becoming a leaking area by a boss such as a deboss which may or may not be used in conjunction with an emboss. The boss or bosses cooperate to seal the area of the gap from leakage. In addition, the carton is designed to provide for very tight corners in which excess material is provided in the blank for closing tightly the corners when the carton is erected for receiving ice cream.

Abstract: An optical scanner scans the surface of printed material at a particular position of the surface to determine if the surface is properly marked. The output level of the scanner at that position is compared with the output level of a differential signal level generator. If the two levels are substantially the same, then no error is indicated. If the two levels are different, then an error is indicated and the process is stopped to correct the error.