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What is Wood Veneer ?
Veneer refers to thin slices of wood
that is usually thinner than about three millimetres or half an
inch. The layers of the Veneer are generally glued and pressed
on to the panels of different kind of materials such as
fibreboard, wood, particle board etc. Veneers are got by the
peeling of tree trunk. The slicing is done through the growth
rings of a tree and the appearance of the figure in the wood
depends on what angle the wood is sliced. Plywood is made up of
a number of veneers wherein each layer is glued at right angles
to the adjacent layers. The contact method that is applying
veneers is fast efficient and cheap. There are different
varieties of contact cement used in veneer that include Weld
wood and Conbond. Veneering is an ancient art used during the
Egyptian times where they used veneers in some of their
furniture.
Slicing equipments or tools used
There are three main types of slicing equipments that are used
for veneer slicing. They are given below.
A slicing machine.
A rotary lathe.
A half round lathe.
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A slicing
machine: A slicing machine is used when a piece of
log is elevated and lowered against the blade of the machine and
slices of log are made.
A rotary lathe: A rotary
lathe or rotary cut veneer is mainly used for plywood since the
form is not desired. It is used where in the wood is turned
against the sharp blade of the lathe and peeled off in one
continuous or semi-continuous roll.
A half
round lathe: Here a piece of log can be moved or
turned into the lathe in such a way that it can be expose to the
most interesting parts of the grain.
Depending upon the pieces of the tree, each sliding process that
are mentioned above gives a very distinctive type of grain. The
other tools most commonly used for applying veneer are a hard
rubber roller mostly the J roller and the other is the Beno that
has three parallel hard rubber rollers with a hammer action
built in it. |
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Material
used for veneering: Generally materials that are
smooth and flat are used for veneering. The materials used are
plywood, particle boards etc.
Preparing the surfaces:
Preparing the surfaces requires patience, practice, planning and
skill. The method of doing so is as follows.The contact glue is
applied to both the surfaces before they are assembled and is
allowed to dry that generally take about ten to fifteen minutes.
Before applying the contacts it should be made sure that there
are no dust or debris on the surfaces. Later i.e. after they are
dried, both the surfaces are joined together and allowed to set.
White or yellow carpenter glues are most commonly used. Once
they are joined it should be seen to that there should not be
any adjustments or any slipping made on it. Veneers can be cut
and trimmed easily even by using a utility knife and a metal
straight edge. Before cutting the veneer it is advised to leave
a margin of error. The extras can be trimmed off later. It is
always better to draw margins with a pencil before cutting.
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Most of the wood veneers have paper
backings that help the glue to stick well and also prevents the
chemicals or solvents of the adhesive from percolating through
the finished side of the veneer. The core material will have an
affinity to absorb the adhesive and leave the weal areas that
will result in air pockets under the veneer. It is always better
to have veneer with a paper backing.
It is advised to have two coats of contact on the back of veneer
and three on the core material and allowing them to dry one by
one before recoating. The contact can be applied by either using
a brush, trowel or roller. The contact can also be applied by
pouring a small amount of contact in the center of the surface
and a knife can be used to pull the contact over the surface as
a thin layer to cover the entire surface of the contact. More
contact can be used if required. The extras on the edges can be
brushed out. It should be done carefully and see to it that the
contact does not pour out of the edges leading it to get
absorbed into the face, however it must be made sure that both
the surfaces are well coated to the extreme edges. |
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Points
to be taken care of
During the preparation of applying the veneer there are two main
objectives that as to be taken care of. One is the sheet
alignment must be on target and the other is to avoid
irreparable air pockets under the veneer. This can be
successfully achieved with slip sheets. A slip sheet is nothing
but a small gauge stiff sheet material that is used as a buffer
or an intermediate surface in between two glue coated surfaces
that will avoid them from contacting and letting you to make any
necessary adjustments before they are contacted.
Procedure
Here is an example of how to veneer a small square slab of core
material.
First thing to be done is the core material is glued and kept
ready leaving about one or one and a half inch along one edge
exposed.
Next a slip sheet is layed over it. Then the surface that is
glue coated is layed over the slip sheet facing down.
It is carefully pulled over the narrow strip of core material
that was left exposed without letting it get contacted at that
point.
The edge of the exposed core material is then aligned with the
pencil line on the paper underside of the veneer.
Little pressure is applied with the thumb on the veneer over
the left hand corner of the core material so that the veneer
makes contact with the point of the core materials corner.
All corners and edges must be checked so that the position of
the veneer would cover the core material completely.
Later the slip sheet is moved one and a half inch backwards
with your fingers from center to left and from center to right
overlapping the strokes in the middle.
Having the slip sheet in original position, run your fingers
over the face of the veneer lightly from the left hand corner
across to the right hand corner so that the veneer and the core
would contact properly driving out any air pockets. This
procedure is repeated about three to four times to make sure
that the veneer is properly contacted with the first one and a
half inch core material.
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Article Contributed By: Shilpa V
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