Casting investments are refractory materials — gypsum-bonded or phosphate-bonded — used to build a mold around a wax pattern for lost-wax casting of metal frameworks, crowns, and removable partial denture components. After the wax pattern is invested and burned out in a furnace, molten metal is cast into the resulting cavity; the investment must withstand high burnout temperatures while accurately reproducing fine surface detail and controlling expansion to compensate for metal shrinkage. Investment selection depends on the alloy being cast — precious, semi-precious, or non-precious — making this a foundational material in conventional metal-framework laboratory workflows.