Chapter 3: Mold Construction:
Traditional Mold Making Methods

This is a brief explanation of all the traditional methods that are useful to the life cast artist. This is a fine art and skilled craft and no attempt is made here to be exhaustive.

The sculpture student is urged to do additional study about these techniques through books, university classes or via our own LifeCast™ Studio classes. Of course, the best teacher is experience. Make something!

Simple Relief Molds are the easiest type.

They are used for objects that are not "in-the-round'. In Basic LifeCasting™ these are used for palm/foot prints, ears, noses, mouths, etc. where the body part is simply dipped into a shallow matrix filled with fluid ArtForm™.

Simple Relief Molds

In more advanced work with the Earthium™ (f/x) relief molds can make more complex designs simple since the work & set times can be so precisely adjusted.

Shelled Reliefs:

These are used whenever you spread thick, paste type application to make the mold. The ArtForm™ or Earthium™ are spread onto the object first. Then, as they set cotton is dabbed over the surface while still tacky. This leaves cotton fibers embedded in the mold surface. Finally a layer of cement or plaster bandages is applied over the mold, binding to it because of the cotton fibers.

Shelled Reliefs:

The entire assembly is removed carefully and the LifeCast™ is poured or Slush Cast as described below.These shells can be reused anytime you encounter a similar design, just take out the flexible and temporary inside mold.

Split Molds:

These are made in the same ways as relief molds but, are usually deeper. One unique characteristic of LifeCasting™ is that we are working with objects that can move themselves out of the mold, minimizing the need for split molds except on very deep designs like entire arms or legs.

They are however, usually required for feet which are split just behind the Achilles' tendon. As the illustration shows you carefully cut the mold (through the matrix or separately) along one side. This allows you to get the object out.

Split Molds:

The split is carefully realigned (and put back into the matrix if split separately) to be filled with a Casting Medium.

Note: The razor blade is symbolic. In LifeCasting™ you would use something which will cut the mold but, not the model. With ArtForm™ and Earthium™ molds a plastic or butter knife work very well without endangering the model.

Sandwich Molds:

These are used when the design is too complex for a split mold or to make several castings from a single mold. Planning and matrix set-up is crucial for multiple piece molds to work properly.

One advantage of our mold compounds is that they can be made not to stick to additional batches. This type of mold can then be made by first mixing enough to cover half the object.

Sandwich Molds:

Alignment notches are then cut, the top part of the matrix attached and the second half poured. When set, the mold is opened as shown, the object removed, the sandwich reassembled according to the alignment notches and the cast made through the pour spout. These can also be made in shelled versions (above).

Contour Molds:

These are made the same as sandwich molds but, the seam is made to follow curved elements of the object to make mold halves that can be pulled straight off.

Contour Molds:

Sometimes these are required by a two piece mold but, more frequently are needed in molds that require 3 or more pieces.

Layered or "French" Molds:

These are made to reduce the amount of mold medium needed on large sculptures. They are typically shelled.
• First the object is covered loosely with a layer of clay. No attempt is made to get the clay into the object's details.
• This layer is "shimmed" for parting seams like a Sandwich Mold and covered with a shell of plaster.
• This gap is then filled with the mold medium. When set the assembly is again removed and the cast object removed.

Layered or "French" Molds:

• The shell is removed along the shimmed, parting seams and the layer of clay is removed. The object is re-centered in the plaster shell, leaving a gap where the clay was.

Slush Casting:

Hollow "Slush" Castings are used with plaster (to lessen the weight), waxes (to be cast in hollow metal) and chocolate (for liquid centers).

With plaster and cement, the wet material is poured into the mold and "worked" up the sides with a spatula or hands as it hardens. The idea is to make walls of consistent thickness.

Slush Casting:

Wax and chocolate will cool from the outside in. When this "skin" is the width you want, pour out the liquid center.
• Another type of slush cast is the "Press" cast where the casting medium is too thick to pour into the mold (see below).

Press Casting can be pressed in with your hands or other tools. The new polymer clays are one example of this and the softer versions can be used in high density (low water ratio) ArtForm™ and Earthium™ molds. – Yet another variation of the slush cast is called the "Ram" cast or die mold. This is used frequently in sheet metal fabrication and high production ceramic and plaster craft industries. The mold consists of two parts; a male and a female.

Each half is the 3 dimensional mirror image of the other with a small gap between them to accommodate the casting medium. The two halves are rammed together with the casting medium in between. This forces the medium into the form defined by the male and female shapes. High production ram dies are made of metal but, are frequently made of gypsum cements such as the ArtCast™ for smaller uses and particularly for ceramics.

Go To Chapter 4: Sculpture & Casting Media:
An overview of contemporary choices.

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