Epson EPI-4000 User Manual page 97

To test paper in the printer, load a single sheet from the package,
run the self test as described in Chapter 1, and look at the results.
Next load another sheet with the opposite side facing up and run
the self test again. Check to see which side gives you the best
printing quality.
See Chapter 7 for detailed specifications on the paper you can use
with the EPI-4000.
Note: Ink jet printers are particularly sensitive to the condition of
your paper. Keep your unused paper in in its original packaging
material and store it in a cool, dry place. Adverse storage
conditions, such as high temperature or humidity, can harm your
paper supply and decrease the printing quality.
Choosing Paper
Paper Handling 3-3