Reply by John Smith

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Posted on Painting MDF

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John Smith

1978 posts in 646 days

#1 posted 01-08-2018 05:19 PM

all very accurate comments above.

fiberboard should not be confused with particle board.
if you really need to know the differences; google ”fiberboard vs particle board”.
both are manufactured from sawmill byproducts using the same manufacturing process.
fiberboard is wood chips and paper scrap that is ground into almost a powder and glued together.
particleboard is only wood chips with a coarse texture and holds more air space than fiberboard.
both are extremely heavy for their size. both are used in the laminated furniture industry.
both can be activated with water or water based products, causing swelling and raised “grain”.
neither one is approved for high humidity applications without the proper preservation.
a diluted solvent based primer should be used to penetrate the board and allowed to cure thoroughly prior
to application of the desired topcoats instead of a waterborne primer.
fiberboard has excellent working characteristics with routing smooth edges where particle board
is less desirable and requires more fillers to make it smooth. (and thin material does not hold fasteners well).
so if you are experiencing finish problems with either, it may be from the initial priming process.
again – waterborne products will raise the fibers and give a less then desirable finish in both products.

Brad – that link to MDF projects is very interesting !!!

on the subject of moisture-resistant Fiberboard and Particleboard, if you really need to use one
for exterior use or in very high humidity areas, there are products used in the sign business
that meet the demanding exterior requirements. . . .MEDEX and EXTIRA are two of them.
Extira and Medex is medium density fiberboard (MDF) that has been specially treated for exterior sign panels.
waterproof glue is used in the manufacturing process. Found mostly in sign supply warehouses, they are probably a special order item at high end lumber yards. these products are EXTREMELY dense and heavy. impervious to moisture and will hold any kind of primer and paint well. very stable in most environments.



-- I am a painter. That's what I do. I paint things --

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