I've just started my first foray into plaster boarding. I'm adding some soundproofing in an alcove next to my fireplace. However, the Knauf Soundboard that I am working with does not seen the break particularly cleanly. I'm scoring with a straight edge, and then snapping the board as I have seen demonstrated in several online videos. However, I never get a completely clean break, with the edge always ending up pitted. Am I not scoring hard enough, or possibly too hard? Or is there something else I should be doing?