Types of moulds explained.
The real key to making an effective mould is choosing the right technique for the job at hand. There are different types of moulds and silicones.
Choosing the right moulding technique and silicone can depend greatly on a number of various factors, namely:
- Material that original is made from
- Purpose of finished product
- Material in which the finished product will be cast in
It is crucial that all of these things are considered before moulding begins. Ensuring that the types of mould and silicone you decide on is best for the job at home
Usually a piece will be suitable for one of 5 main categories of mould:
A poured mould is also known as a “Flood Mould’ or “Block Mould”.
This is a very simple technique that is most suited to solid pieces that are either flat, or long and thin, and not overly complex in their shape – like a plaque or a bottle, for instance.
In this technique, the piece is securely fixed to a base, and walls built around sealing the piece within.
The silicone or other moulding material is then poured around the piece completely covering it.
Once the silicone is set the walls are removed and the piece can then be released from the mould, usually via a release cut done with a scalpel.
This technique is very quick, easy and leaves very little by the way of a seam line.
Painted moulding is also referred to as a “Jacket Mould”.
This style of mould making is best suited to larger more complex pieces, such as sculptures, where the elements are irregular or fragile.
With this technique, the mould maker paints on layers of silicone to build up a ‘skin’. Once the skin is thick enough, a rigid ‘jacket’ is then created over the skin.
The job of the jacket is to support the skin in its correct position.
The number of jacket parts will depend on the complexity of the original piece. The rigid jacket is usually made from plaster or fibreglass.
Once the jacket is complete, the jacket parts are removed and the skin cut to release the original.
This technique works best for fragile items as the skin is quite thin and can be peeled away from the piece without putting too much pressure on any one part, thus lessening the chance of breakage
Also known as a “Group Mould”. A gang mould is best suited for many small identical items.
A group of small items is arranged for best use of space, then a wall built around.
The mould is then filled in the same way as a poured mould.
This style of mould making is good for small parts, or even chocolate moulds.
A Matrix mould
Matrix moulding, or matrix transfer moulding is a technique where the mould maker will first create the outer rigid shell leaving a small gap all the way around the piece.
After the shell is complete, the silicone is then poured into the gap, thus encapsulating the original and gripping the outer shell.
This process is best suited for pieces with lots of deep detail or texture.
Traditional Lay Up Mould
This technique usually works best when using rigid moulding compounds such as plaster, such as for slip cast moulds, or fibreglass for casting silicones or flexible urethanes – like for masks or prosthetics.
This technique is very time consuming and leaves part lines all the way around the original object, so must be done with absolute precision.
If the parts aren’t divided exactly at the right angles/positions, the mould can lock shut and will have to be broken in order to release the original piece.
The more complex the original, the more pieces the mould must be made in.
Each section must be built up and separated from the rest of the model in order to pour a section at a time.
For some more examples of the different types of moulds and silicones in action check out the gallery.
In the next post I’ll be covering the different types of silicones used for moulding.