If you are new to mould-making and casting, this is the page for you!

I have listed many of the words and terms, together with their meaning below to avoid confusion.


Activate- The process of adding one liquid to another to initiate physical change (usually the addition of a catalyst to another substance.)

Addition polymer- The chemical mechanics of the change induced by the catalyst. Does not work well with condensation polymers.

Catalyst- Usually liquid (can be powdered) volatile chemical causes an intentional reaction with another substance to change physical properties. Usually liquid to solid.

Cast- Production of a copy of the original shape. A replica.

Condensation polymer- The chemical mechanics of the change induced by the catalyst. Does not work well with addition polymers.

Cure- The process of 2 or more chemicals reacting to produce 1 substance.

Filler- Any dry non-reactive (inert) substance used to saturate a resin to change texture, colour or resistance to heat/cold.

Inert- Non-reactive substance, harmless material.

Inhibition- Undesirable effects of one substance on another causing one or both materials to fall short of achieving full physical properties.

Isocyanate- Volatile substance, known to cause cancer with over exposure amongst other affects. One of the two parts of Polyurethane compounds. The other is Polyol.

Jacket- A rigid supporting structure made from Fibreglass or Mod-roc. Used with soft skin moulding materials like silicone or latex. 

Laying up- Part of the fibre-glassing process involves the layering of strips of glass fibre soaked and bonded together with polyester GP resin.

Master- The original object that will be moulded and cast to produce a replica.

Mother mould- See Jacket.

Mould- A negative impression of the Master. Used to produce a cast.

Multi part mould- Advanced mould making technique using 3 or more pieces to form one mould. Used to produce complicated castings.

Open mould- Simple one-piece mould making method used to produce simple shapes.

Plug section mould- Fairly involved process usually made with rubber, used to capture inner and outer detail such as that of a cup or glass.

Polymer- Large molecule made of many adjoining parts such as that found in plastics and some natural materials like animal shells and horns.

Polyol- One of the two parts of polyurethane. Less harmful partner of Isocyanate.

Prosthetics- An artificial extension of the human body often using rubber/ foam.

Release agent- A barrier layer acting to separate one surface from another to prevent one sticking to another.

RTV- Room Temperature Vulcanizing, a process of curing rubber, coined by the inventor Charles Goodyear (like the tyre he later invented).

Shore hardness- A valuable scale used to measure the hardness of a substance. 0 is the softest 100 is the hardest. Shore A hardness used to describe foams and rubber. Shore D hardness is used to describe plastics.

Skin mould- Fairly involved method of mould-making using rubber. Commonly used to replicate large sculptural works or complicated shapes as a one piece mould. Needs support of a jacket.

Slip cast- A hollow reproduction of the original Master.

Split mould- A simple way to capture the detail of an entire surface of an object using rubber.