Acrylic Sheet, Rod and Tube: Cast and Extruded

Acrylic (PMMA) stock is made two ways. Cast acrylic is liquid methyl methacrylate, mixed with an initiator, poured between glass plates (cell casting) or into moulds and left to polymerise into solid sheet or rod; tube is cast in a spinning mould. Extruded acrylic is pellets melted and forced through a die and polished rollers, continuously. Cast sheet is the better grade: steadier with heat and solvents, clearer, more scratch resistant and better to machine; extruded sheet is cheaper and more even in thickness.