Xerox 4090 - Manual (Page 148)

PAPER
Table A-1. Paper conditioning
For example, if you want to move 10 cartons of paper from a
storage area with a temperature of 90 degrees F to an operating
area with a temperature of 75 degrees F (a 15-degree difference),
you should do so at least 14 hours before using the paper.
Paper curl
Before paper is cut into sheets by the manufacturer, it is stored
on large rolls. After it is cut and packaged, it retains some of the
curl from the rollers.
Although it is unnecessary to load paper with the curl specifically
up or down, best results occur when you are consistent. For
example, if you open paper with the wrapper seam up, always
load it in the tray that way.
A-4 XEROX 4050/4090/4450/4650 LPS OPERATOR GUIDE