I've noticed that the prefab counter tops sold by Home Depot (and others) here in Winnipeg have curvature to them which I don't notice in installed plastic laminate counter tops. Specifically, the curvature that I'm referring to is the front-to-back curvature so that if you were to lay a straight edge from the front bullnose to the rear backsplash of the counter top, you'd see a gap between the straight edge and the counter top. I've been told that this curvature is called "cupping". I've also been told it's caused by: 1. the plastic laminate shrinking as it cools, and 2. the particle board swelling as it absorbs moisture from the air. Does anyone know of a web site or other source that would establish with certainty what this curvature is called and what causes it?