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Veneers may be made either from softwood or
from hardwood. Plywood manufactured from veneer from softwood is
more durable than that made from hardwood. Plywood made from
hardwood veneer however wins hands down where appearance is
concerned.
Veneers vary in thickness depending upon
the purpose for which the ply is to be used. Thicker sheets of ply
will need thick sheets of veneer. The thickness of the veneer strips
generally varies from 0.09 cm to 0.32 cm. Once cut, the sheets of
veneer are dried and trimmed. These are arranged in layers and glued
together. The topmost layer and the back layer are usually made up
of single sheets of veneer. Smaller sheets of veneer are used for
making up the inner layers of the sheet of plywood. This inner layer
is referred to as the core. The number of layers in a sheet of
plywood can range from three to nine. Plywood that is used for doors
generally has a core that is up to three inches thick.
The process
Several layers of veneer (the number depends upon the required
thickness) are sprayed with adhesives or adhesives are applied using
rollers. Adjacent sheets are placed in such a way that the grains of
one layer are perpendicular to the next layer. This ensures that the
sheet of wood that is readied is exceptionally strong for its
weight. The panels of veneer thus stacked together are pressed at
specific temperatures. This needs to done with due care so as to
rule out any weak spots that may result in the plywood falling apart
later.
Why plywood is preferred
Plywood does not generally warp, shrink or split. It is strong
and also flexible to a certain extent. Its flexibility ensures a
certain amount of ease of bending without the danger of splits,
cracks or breaks. As compared to wood, plywood is cost effective.
This is because the core can be made up of less expensive wood, thus
bringing down the cost. Plywood is stronger than a wooden board of
the same thickness. As veneer are extremely thin strips they dry
very fast, so dry plywood can be made even from moisture-laden logs
of wood.
Some precautions
The glue used for sticking layers of veneer together should be
of good quality to avoid the layers peeling off. Some amount of
termite protection also needs to be given to avoid the danger of the
plywood falling apart due to termite attack. Plywood that is
intended for use in water, e.g., in boats, should be made using
water-resistant glue.
How old is plywood?
Plywood was used to a certain extent in ancient China and Egypt.
However, chairs made of veneer strips were seen in Germany in the
1800s. Plywood is believed to have made its appearance in the United
States in 1865. It came to be used extensively only after 1900.
Particleboard and fiberboard are later
entrants in this field and are preferred over plywood by many
because they are more durable. |
