If the boards of polystyrene construction and glassed with epoxy resin a few signs are 1, its superlight weight , 2 it should be written on the board somewhere that it is epoxy construction,3 alot but not all epoxy boards will be stringerless.4 if you can see the foam of the board and it is polystyrene it must be filled with epoxy resin
A general rule is if you are unsure of contruction use epoxy resin as it will not harm a PU board but never the other way around .PU on a,polystyrene board will trash it👍
Hey Simon, what are the telltale signs that a board is Epoxy or PU construction