Acrylic options include both cast and extruded acrylic. Cast acrylic, when engraved turns a frosty white color. This type of sheet is made from a liquid acrylic that is poured into molds. Extruded acrylic, when engraved makes for clear engraving. This type of sheet is made on a large, high-volume manufacturing extruder that forms the liquid plastic into sheets in a continuous fashion.