What Mould-making technique should I use?


There are lots of ways to make moulds, all of which use very different construction and application techniques depending on what you are moulding and what your end objective is.


Although I have identified 5 main ways to make a mould, there are no set rules to mould making and many of these methods can be combined, indeed, they often rely on using one technique with another.


Awareness of these different methods will help you understand their relationship to each other.

Mould-making-

   

   

Single part open mould-making

Plug section mould-making

 

There are many different ways to make mould.

Below are 5 of the most commonly used methods used for small scale reproduction.

Most methods can be combined with one another easily.

 

What is a Multipart mould?


Multi part moulds are a very versatile form of mould making, in that, it is possible to make a multipart mould for many different complex sizes and shapes. Multipart moulds can also be made from a number of different mould making materials such as fibre-glass, plaster, silicone, polyurethane rubber, or latex.


This type of mould making is best suited to complex shapes that curve on multiple plains of space. A multi-part mould commonly involves other methods of mould making, especially skin mould making techniques. For example; a skin of silicone maybe applied before a multipart jacket is added. This combination ensure that detail is preserved by the silicone while the multi-part jacket supports the form.

What is a Plug section mould?


A plug section mould is technically a two part mould (or multipart mould) with a specific purpose, made in a particular way where it is possible to cast the inside and outside of an open compound form, such as a glass or cup.


This type of mould making is the best way to reproduce castings with thin or delicate shapes. It is also a great way of capturing surface detail on the inside and outside of an object.

What is a Single part open mould?


This is one of the simplest forms of mould making. This method is not suitable for larger castings or shapes with large undercuts. We can use a number of different materials to make this kind of mould, such as latex, polyurethane rubber or silicone even gel-flex. Due to the nature of this type of mould we must always use a flexible material. This allows us to flex the mould to remove the castings easily.


The advantage of this type of mould-making is that casting material can be applied in stages allowing for marbling and layering of resin, slip casting and embedding or encapsulation. It also allows water content in water-based casting materials, such as plaster, concrete and cement, to evaporate more readily.

What is a Split mould?


A split mould is a great way to cast complex shape of small to medium size quickly and effectively. This method is virtually identical to the one part open mould making technique (above). It is essentially a one-part mould with strategic splits cut through it post cure. These splits allow for greater complexity of shape to be used because the rubber mould (usually silicone) can be stretched open along the splits to extract the master and the subsequent castings from the mould. This method is commonly used when casting figurines and action figure prototypes.


This technique sometimes requires the use of air vents to assist in evacuating the air pockets that are caused and trapped by certain shapes. Although initially more difficult and longer to prepare, moulds with air-vents are likely to produce higher quality castings than plain split moulds without them.

   

What is a Skin mould?


Skin moulds can be made to almost any size and shape and is one of the cheapest and most versatile forms of mould making. However, it is also one of the most complex and involved mould making methods. This technique is commonly used in industry for reproducing large statues and interior décor features.


A skin mould can be made with silicone, latex or polyurethane rubbers. When using latex to make a skin mould (dependent on the masters surface porosity) it can be dipped or brushed on to build a skin thickness around the master prior to a jacket being added.


Silicone and polyurethane must be poured and spread on to achieve a skin thickness.

Skin mould-making

   

Split mould-making

   

Multipart mould-making