flat surface, everything will appear OK.
However, wherever there is a pimple
in the MDF, the veneer will be raised.
Now when sanding the panel prior to
finishing, there would have been a lot
of the veneer sanded off right at the
pimple (that is, the veneer would now be
thin) and the MDF would be close to the
Now, when we use a waterborne stain,
the moisture that goes into the MDF in
these “thin” spots causes the MDF to
swell a little bit in these localized spots.
This swelling will show up as a bump or
pimple in the finish.
The cure is in the manufacturing of
the MDF. Although the waterborne finish, which is so common today and must
be considered by all manufacturers, is
part of the scenario, to blame the WB
finish is like blaming the hard ground
for causing the sudden stop when you
jump out the fifth floor window. Without the waterborne finish, the bumps
might not have been as dramatic and
would not have showed up promptly
after finishing, but would eventually
show up later in the customer’s home
Incidentally, we see the same
pimples when using a solid wood core
with a veneer lamination and even with
solid wood itself. In this case, the wood
was planed smooth using an inadequate dust system. The chips hung on
the knives and compressed localized
areas when they rubbed on the surface
of the wood. Although the surface can
be sanded smooth, the compressed
areas were too deep to be sanded off
and so they will pop up later, especially
with moisture. ;
704.799.0100 • www.weinigusa.com
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