< INVESTMENT SUMMARY
INVESTMENT KEYWORDS
CERAMIC SHELL: A refractory investment system used for lost wax casting. A wax assembly is coated with a ceramic slurry and dusted with fused silica grits. Successive layers are built up until the refractory mould reaches a sufficient thickness to allow wax removal and casting.
CHARGE: Quantity of metal alloy for pouring into a refractory mould.
CIRE PERDU: (Fr.) ‘Lost wax’.
COLLOID: Minute particles of electrically charged material (silica for the investment process described here), dispersed in a ‘sol’. Silica sol – a water based colloid, or ethyl sol – an alcohol based colloid, function as a refractory binder.
CORE: A refractory mass suspended within an investment (or sand) mould. After wax removal, the core maintains an air gap into which molten metal is run to enable a hollow cast to form.
CORE VENT: A tube set into the core interior which is extended through the outer investment out the atmosphere, allowing evolved cavity gases escape during casting.
CORE PINS: Metal pins for locating and fixing a core in place relative to the outer investment wall.
DE-WAX: See WAX BURNOUT.
DRAIN: An aperture in the investment mould, designed and place on the wax pattern to allow wax to escape the mould cavity during kiln burnout.
FLASK: Metallic container sleeved over sprue trees etc to contain liquid investment. May be perforated to assist the even application of a vacuum force.
FUSED SILICA: A fragmented refractory body of variable grit size used to build up of a wall thickness in ceramic shell investments. Referred to as a STUCCO in the larger mesh sizes, FLOUR in the finest.
GROG: Crushed, fired and graded fireclay refractory.
HEAD: Typically, the top end or entrance into a mould.
HYBRID INVESTMENT: A specialist method of investment mould construction, combining different moulding techniques and refractory systems, typically plaster & grog, ceramic shell, and hard set sand.
INVESTMENT: The refractory material or materials used to create a thermally resistant mould suitable for metal casting by the lost wax process. The word may also be used as a verb to describe the overall process of forming a mould.
INVESTMENT MOULD: Any mould which encases or ‘invests’ a lost wax type pattern in advance of casting.
JEWELLERY CASTING: The casting of (typically) small intricate wax patterns, usually vacuum or centrifuge assisted.
MESH SIZE: Scale for grading refractory investment and sand particulate etc. The larger the mesh number the smaller the grit size.
OPEN CORE: The omission of a solid core mass for layers of ceramic shell to create a hollow metal cast.
PLASTER OF PARIS: Calcium sulphate hemihydrate/gypsum, an important material both for patternmaking, and as a foundry refractory/binder.
REFRACTORY: Materials (esp selected minerals) highly efficient at resisting the effects of thermal attack.
REFRACTORY MOULD: A general term which may include both investment and sand moulds.
SLURRY: Refractory flour suspended in colloidal sol (ethyl or silica), to create a fluid ceramic preparation.
WAX BURNOUT: Removal of wax from an investment mould by the application of heat (in a kiln or autoclave), or by solvent washing.
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