A lampshade includes a self-supporting backing member constituted of an extruded oriented polystyrene and an additive including a light-reflecting powdered filler, especially titanium dioxide, co-extruded with the oriented polystyrene and weighing in the range of 1%-10% of the total weight of the polystyrene....http://www.google.com.au/patents/US5858488?utm_source=gb-gplus-sharePatent US5858488 - Hard-backed lampshade
