Appendix A - Definitions
Knowing the meanings of words is important to anything you do. Mold making and casting has a number of unique words to the craft and here we try to clear some of the fog that may arise by supplying a few definitions.
- Accelerator
- A substance which increases the rate of cure.
- Alginate
- Any of several derivatives of alginic acid derived from seaweed or sodium alginate reacted with calcium salts for making masks and castings.
- Alloy
- To mix, as metals, so as to form a compound.
- Block Mold
- A term used in mold making to describe a mold in which the silicone completely fills the area between the master and mold support. The exterior of the mold does not conform to the shape of the master.
- Casting
- To form (liquid metal, for example) into a particular shape by pouring into a mold.
- Catalyst
- A substance used to significantly accelerate a chemical reaction.
- Concrete
- A hard, strong construction material consisting of sand,conglomerate gravel, pebbles, broken stone, or slag in a mortar or cement matrix.
- Cure Time
- The time a sealant takes to develop its full properties.
- Curing
- To prepare, preserve, or finish (a substance) by a chemical or physical process. To vulcanize (rubber).
- Degassing
- To remove gas or air from.
- Die Stone
- A dental product made from gypsum that has a compression strength usually over 18,000 PSI.
- Form
- A mold for the setting of concrete, plaster, silicone or other agent until it cures.
- Gypsum
- A widespread colorless, white, or yellowish mineral, CaSO4·2H2O, used in the manufacture of plaster of Paris, various plaster products, and fertilizers.
- Latex
- An emulsion of rubber or plastic globules in water, used in paints, adhesives, and various synthetic rubber products.
- Ladle
- A vessel to carry liquid metal from the smelting pot to the mold.
- Lead
- A soft, malleable, ductile, bluish-white, dense metallic element, extracted chiefly from galena and used in containers and pipes for corrosives, solder and type metal, bullets, radiation shielding, paints, and antiknock compounds. Atomic number 82; atomic weight 207.2; melting point 327.5°C; boiling point 1,744°C; specific gravity 11.35; valence 2, 4.
- Library Life
- A term referring to the length of time a mold can sit in storage with deteriorating.
- Master
- Being an original from which copies are made.
- Mold
- A hollow form or matrix for shaping a fluid or plastic substance.
- Mold lines
- Lines showing up on the finished cast caused from molds made up of two or more pieces.
- Naphtha
- Any of several highly volatile, flammable liquid mixtures of hydrocarbons distilled from petroleum, coal tar, and natural gas and used as fuel, as solvents, and in making various chemicals.
- Negative
- The reverse impression of the master that is left in the mold.
- Pewter
- Any of numerous silver-gray alloys of tin with various amounts of antimony, copper, and sometimes lead, used widely for fine kitchen utensils and tableware.
- Plaster
- A mixture of lime or gypsum, sand, and water, sometimes with fiber added, that hardens to a smooth solid and is used for coating walls and ceilings or casting figurines and other items.
- Potlife
- The term referring to the cure rate of a silicone RTV.
- Pressure Casting
- A casting technique of using compressed air in a pressure pot to reduce or help eliminate air bubble from castings. Typically used when casting resins.
- Pressure Pot
- A specially designed container for casting under pressure.
- Pulls
- An expression referring to the number of parts obtained from a mold.
- Release Agent
- A compound or solution to allow a newly cast object to be released from it's mold. Or to keep the original from sticking to the mold making material.
- RTV
- RTV Silicone are a rubber like polymer called polydimethsiloxanes. RTV stands for room temperature vulcanizing, or simply a rubber which cures at room temperature. Silicone rubber adhesives are made from a complicated process that turns elemental silicon metal made from sand (silica) into a rubbery polymer. When cured, silicone rubber adhesives/sealants have excellent resistance to heat (500-600ºF) and moisture which makes them exceptionally suited for outdoor weathering applications, such as sealant and caulking compounds in the construction industry. A silicone rubber usually of a two part composition which cures at room temperature. RTV silicone moulds typically yield upwards of 100 or more casts with incredible detailed reproduction of the pattern.
- Shelf Life
- The amount of time a product may be used without deterioration.
- Shore Hardness
- A scale of measurement used to describe the hardness of a material when measured with a durometer. There are three commonly used scales, in degrees of increasing hardness: Shore 00, Shore A and Shore D.
- Slip Mold
- A mold usually made of latex that when filled with casting media is pulled off the casting like a slip.
- Smelt
- To melt or fuse (ores) in order to separate the metallic constituents.
- Split Mold
- A two piece mold used to create castings that could otherwise not be made with a single mode or slip mold.
- Tear Strength
- A test technique used to measure the force required to initiate or propagate a tear into a material sample, measured in pounds per inch "PPI".
- Tensile Strength
- A method to measure the force required to rupture the material (stress-strain at break) per unit area subjected to a specific dynamic load, usually expressed in pounds per inch.
- Tin
- A malleable, silvery metallic element obtained chiefly from cassiterite. It is used to coat other metals to prevent corrosion and is a part of numerous alloys, such as soft solder, pewter, type metal, and bronze. Atomic number 50; atomic weight 118.71; melting point 231.89°C; boiling point 2,270°C; specific gravity 7.31; valence 2, 4.
- Undercuts
- A term describing the complexity of a shape; these areas are very deeply indented or cut, and therefore require that the mold be pulled and stretched around them in order to remove the mold.
- Vacuum
- A space in which the pressure is significantly lower than atmospheric pressure.
- Vacuum Chamber
- A Specially designed chamber that is designed to hold a vacuum.
- Vacuum Pump
- A mechanical device designed to remove air from a vacuum chamber.
- Vaseline
- A yellowish translucent substance, almost odorless and tasteless, obtained as a residue in the purification of crude petroleum, and consisting essentially of a mixture of several of the higher members of the paraffin series. It is used as an unguent, and for various purposes in the arts.
- Vent Channels
- Channels cut into a mold to allow the escape of air.
- Viscosity
- resistance of a liquid to sheer forces (and hence to flow)
- Wet Water
- Water that has had a small amount of liquid soap mixed in with it to reduce the surface tension of the water.
- Worklife
- A term used to indicate the amount of time an end user has to work with a curing silicone.