Learning the Mold Making/Casting Lingo

What is the negative image of a model called that you will make before making a positive replica? What are the holes on the top or bottom of a mold called? Know the terms that go with molds and casts right away!

The world of mold making, casting and life casting comes with its own plethora of terms and phrases. Familiarity with them is essential.

  • Mold – It is a negative impression of the model, usually in the form of a hollow cavity.
  • Cast – This is a positive duplicate of the model which can be in any other material or color as desired.
  • Cold cast – This is a faux cast – it is made of resin but can duplicate the look of metal, stone or wood.
  • Life cast – The three-dimensional representation of a live person – it can be the face, hands, feet, torso or entire body.
  • Pot time – Also known as working time, this is the time on hand to work with a material – it includes the mixing and application time - before it will start to set. After this, the material will not work properly.
  • Cure time – This is the time that the material will take to get completely cured. It can range from just a few minutes to hours or even a few days.
  • Shelf life - The period of time a material can be stored and remains suitable for use.
  • Mix ratio - The proper proportion (either by weight or volume) of material and catalyst (oftentimes referred to as Parts A and B) to be combined.
  • Shore hardness – This is a measure of the hardness of a given material or how resistant it will be to permanent indentation.
  • Release agent – A material applied in a thin layer to the surface of the model or mold so as to allow the subsequent mold or cast to be demolded easily.
  • Sealer – Another material that is applied on porous models to seal the pores and prevent the mold making material from getting absorbed.
  • Demolding – The process of removing a model or casting from a mold.
  • Parting line – A marking line which denotes where the parts of the mold should meet.
  • Keys – These are created at the ends of multi-part molds to join the different parts together to form a complete mold.
  • Spues – These are the small holes which will help release the air trapped inside the mold.
  • Pour hole – This is created as an opening to allow the casting material to be poured into the mold.
  • Viscosity – This is the thickness or thinness of the material and will dictate how easily it will flow. Less viscous materials are thinner and flow easily.
  • Pressure pot – Resins are usually cast under pressure that will compress the trapped air to miniscule size.
  • Vacuum chamber – The rubber mix is usually churned using a vacuum pump with vacuum chamber. The vacuum chamber will suck out the air and not allow bubbles to appear on the rubber mold or cast.

Armed with this detailed knowledge, get going right away!

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