Wood Veneers: Which Glue To Use?
There are many adhesives on the market. Which
one you chose for gluing down wood veneers is dependant upon your
equipment, experience and skill. For the purpose of our small crafters,
we'll only discuss three types, the traditional "hide"
glue, the off the shelf Contact Cement and standard PVA water based
carpenter's glue.
Hide Glue:
This is the traditional glue that has been
used by wood veneer craftmen for generations. It is typically bought
in pellets or flakes, relatively cheap and has an indefinite shelf
life in its dry form. It is water soluble, thus easy to clean up,
and has a long working time. If fact hide glue can be reheated to
allow movement or disassembling of your project (a feature often
used in the repair of violins).
Its main disadvantage, is the messy process of
mixing it with water to the right consistency and heating it to
use. It is not great as a table top adhesive, since a hot dinner
pot or excessive moisture, would disengage the veneer. Many craftsman,
do not like to use it because of its dark colour that can show through
lighter coloured veneers. Lastly, if the glue mixture is made with
excessive water, it can cause the veneer to expand on initial layup
and then shrink on drying.
Bottom line is that craftsman typically use hide
glue for historically correct restoration projects, when they need
a long open time, or when it may be important to take the project
apart at a latter date....... otherwise they will use newer glues...
Contact Adhesives:
are an easy and fast way to glue down veneer,
but the results can be somewhat inconsistent. Success depends on
a rubber glue line which is very stretchable and allows movement.
It can not be used successful in any situation where multiple pieces
of veneer are joined together for a fancy inlay table... the pieces
tend to shift,..... but can be great on one piece glue ups. Remember
that once the veneer has been put in place, you can no longer alter
its position...so aim accurately the first time... its a one shot
deal.....
It is important to consider compatibility of the
contact glues with the finish. Some finishing materials can chemically
break down the rubber bond of contact adhesives. Lacquer finishes,
for instance, can actually melt the rubber glue line. Do a test
run before you start.
The advantage of contact cement, is that it does
not require clamping of any sort. This is particularly important
if you are trying to apply a veneer to an oddly shaped, small piece
and require instantaneous bonding. Since contact cement is resistant
to heat it is also a good choice for 1 piece lamination onto a table
top.
For multi piece marquetry, or fancy seaming of
wood veneers, PVA glues are a better choice.
Carpenter's Glue-PVA: (polyvinyl acetate)
This is an easily available glue, for general
purpose woodworking. It is waterbase, and sold in various brand
names, dry times and qualities. Once it is dry it does not shift
and unlike a contact cement, is easy to spread in uniform layers.
It is readily available and has a long shelf life, although I have
seen it mold if stored in an excessively hot environment.
In our production shop we always use a high
strength, high viscosity (thicker) PVA glue, for wood lamination.
..... but in wood veneering this is not necessary. Most cheaper
glues are thinner (ie more likely diluted), but this is an advantage
in this case, because it allows a thinner, more even/uniform layer
to be applied to the substrate.
You don't need high strength when all you're
trying to do is stick down a 1/32" veneer to a piece of MDF......
just use your standard woodworkers glue and I'm sure you'll be happy
with the results.
PVA glues do require a clamping method to
hold the wood and/or veneer in place while drying, often this can
include some sort of press arrangement, or vacuum bag.
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