Multilayer polymeric shells for spas, bathtubs and shower enclosures having a textured and marbled surface layer. The shells are produced by forming by extrusion a multilayer polymeric sheet having a marbled appearing top layer, passing the sheet between rollers to impart a textured surface to the marbled...http://www.google.co.uk/patents/US6231938?utm_source=gb-gplus-sharePatent US6231938 - Extruded multilayer polymeric shell having textured and marbled surface
