40 ENWW
curl The amount of curvature or wave in a sheet before or after printing. Sheets might
curl before printing if they are exposed to humid conditions or very dry conditions.
Residual stresses in the sheet or high moisture content can also affect the level of curl
after printing. Good process control by the paper manufacturer and proper paper
storage and handling will minimize curl problems.
Curl is typically measured by laying the sheet of paper on a flat surface and measuring
the height of the corners. There are two types of curl:
• In-ream curl is the amount of curl in a sheet of paper before printing. In-ream curl
results from the paper-manufacturing process or from exposure to the environment.
Paper with excessive in-ream curl might lead to feeding and print-quality problems.
• Post-image curl is the amount of curl in a sheet of paper after printing. Post-image
curl results from exposure to the fusing process and the paper path in the printer.
Paper that has excessive post-image curl can be difficult to handle or to use in
automatic-feed photocopiers.
cut-edge condition Condition of the edges of paper, which can affect paper’s ability to
feed properly.
cutouts Any portion of the media that has been removed, including binder holes,
notches, square cuts.
density Relative darkness of the print.
die-cuts Cuts between individual labels. Die-cuts are made by a machine in a
predefined pattern.
duplexing Printing on both the front and back sides of a sheet of paper.
electrical properties The electrical resistivity of the print media. The electrical resistivity
of the paper is one of the most important properties for copier- and laser-grade
papers. If resistance is too high, static buildup problems can occur with paper handling
and print quality. If electrical resistivity is too low, poor image transfer and low density
can result. Generally, paper has very high resistance, so paper manufacturers add
salts or other materials to lower the resistivity.
face sheet The face sheet is the printable surface on a sheet of adhesive labels. It can
be made from different materials, including paper, polyester, and vinyl. It is common
for a face sheet to be die-cut so that individual shapes can be removed after printing.
Polyester and vinyl labels require a topcoat to provide the proper electrical and toner
adhesion properties. It is important to purchase labels from a knowledgeable supplier
who is familiar with these processes and with laser printing.
felt side versus wire side Some methods of manufacturing paper result in two-sided
paper that has properties that differ from one side to the other. Along with other
process variations, these properties can make one side of the paper the preferred side
on which to print. The “top” side of the paper sheet, as it is formed, is known as the felt
side. The “bottom” side is known as the wire side. Most manufacturers indicate the
preferred printing side on the package. See “Reading a ream label” on page 5.
