Deinking
Sometimes the pulp must undergo a “pulp laundering” operation called deinking (de-inking) to
remove printing ink and “stickies” (sticky materials like glue residue and adhesives). Papermakers
often use a combination of two deinking processes. Small particles of ink are rinsed from the pulp
with water in a process called washing. Larger particles and stickies are removed with air bubbles in
another process called fl otation.
During fl otation deinking, pulp is
fed into a large vat called a
fl otation cell, where air and soaplike
chemicals call surfactants are
injected into the pulp. The surfactants
cause ink and stickies to
loosen from the pulp and stick to
the air bubbles as they fl oat to the
top of the mixture. The inky air
bubbles create foam or froth which
is removed from the top, leaving
the clean pulp behind.