Backgrounds and flash ?

Got a question , I'm receiving a photo trigger splash art kit soon and want to have very clean backgrounds now iv read in a magazine that featured this very kit about using white acrylic , my question is will a speedlite acctually flash through 3mm white acrylic as its supposed to be lit up from behind as the magazine suggested as I can't see it happening as its solid white for a reason or have they more than likely used trans/frosted white which would make sense .