GLUING & PRESSING
Warp is seldom a problem with com-
posite panels when care is taken. To
prevent warp in flat laminated panels:
1. Store panels and laminates
in reasonably uniform, protected
warehouse conditions, avoiding
extremes in temperature and humidity
2. Balance the overlay sheets by
type and weight, and ensure they are
evenly conditioned. The ideal is 70F
(± 5) and 35% (± 5) RH for one week.
3. Be sure the grain and machine
direction of the paper run the same
way on both sides of the substrate.
4. Be sure that press conditions
are set to properly cure both sides
when using different papers.
5. Whenever possible, utilize a
balanced construction with uniform
temperature for both the top and
6. Use as few openings in the
press as possible: too many openings
may increase the precure by slowing
the closing time.
7. Stack hot boards flat in
covered piles and allow them to cool
to 120F or less before sawing.
Causes of warp in veneered panels:
1. A very thin core with thick
2. Unbalanced glue spreads on
the two sides of the core. Also too
heavy a glue spread or too low glue
solids content. Inadequate cure of the
glue in the hot press can also cause
6. Pressing two thin panels in one
opening or uneven heating of platens
within or between openings.
7. Different moisture contents,
species density or thickness of face
veneers can unbalance the panels.
Source: Composite Panel Association,
703-724-1128. More information is
available at CompositePanel.org. Also visit
Preventing warp in flat surfaced panels