Cast acrylic, when laser engraved, turns a frosty white color. Cast acrylic sheets are made from a liquid acrylic that is poured into molds that are as large as 4 feet X 8 feet in size. These large sheets are molded to several thicknesses from a thin 1/16-inch to a beefy 1-inch thick.
Extruded acrylic is another type of commonly found acrylic. A large machine much like a printing press forms the liquid plastic into sheets in a continuous fashion. This high-volume manufacturing technique makes the sheets of extruded acrylic less expensive than the casting method. Note that the different raw material used for extruded acrylic makes for clear engraving when lasered. Although not always ideal for engraving applications, extruded acrylic cuts superbly with a laser. Extruded acrylic cuts cleanly and smoothly with a flame-polished, glass-like edge quality.
-Mike Fruciano, Coherent