Sealing MDF

[John Johnson 2]

What is the best way to seal MDF for outdoor signage use?

[Neal Schlee]

What is the best way to seal MDF for outdoor signage use?

John, it's not good practice to use MDF for exterior signage, Extira is the way to go.
http://www.extira.com/pageBuild.asp?PageID=B_signmaker_e

Neal

[Ray Mighells]

MDF is not practical for outdoor use. You could bury it in casting resin but I wouldn't guarantee that either.

[Michael Hunter]

West System epoxy (as used for wooden boats) will make MDF last outdoors for years and years.
The epoxy is really expensive for this sort of use - better to find a more water resistant material to start with.

[Paul Grothouse]

Best way to seal it - get exterior grade MDF. West is not suitable alone on regular MDF, the binders will fail, it will go from 3/4" to 2" thick in one season.

[Joe Pelonio]

MDO is a much better choice for outdoors. MDF is cheap but not meant for outdoors.

[Mark Conde]

Marine Epoxy/varnish would seal it up. Although like others have stated MDF. I have good success with MDO (medium density overlay) it is impregnated with tons of resin to resist the exterior elements.