Monthly Archives: May 2011

The How and Why of Silicone. (Part 2)

HOW TO CHOOSE YOUR SILICONE    

Ok, so you have your project ready, you are off to go buy some silicone and dive right in….  Whoa!  Slow down, tiger….. There is a whole bunch of stuff you need to know first.

What are you doing?  Is it a big piece, a small piece? Are you making a mould or a cast?  Do you need to make a box mould, a brush-up mould, a matrix mould, a pour mould?  How much are you going to need to fill it?  Do you want a solid coloured, or translucent  silicone? Are you in a hurry or is time not an issue?  Will you need a long or short Potlife?  What sort of Viscosity is required? What Shore Hardness do you require in your finished piece? Do you need to worry about Elongation/Tear Strength/Tensile Strength?

Yeah, working with silicones is a bit like  doing high school chemistry all over again, but trust me, if you understand the basics, it will save you a lot of time, money and frustration.

Lets start with the Product Description. 

When you are searching a website for silicon moulding rubbers, you will usually find somewhere a link to a.pdf saying “Technical Data Sheet”, “Product Overview”, or the like.  In a catalogue there may be aTable giving comparisons between the products on offer.

Note that the information I am discussing here is NOT on the MSDS… (the what? I hear you say? It stands for the ‘Material Safety Data Sheet’- a topic for another time…).  

A Technical Data sheet will give you all of the relevant information you need about a product. Lets go through one step by step, just to give an example.

At the top there will normally be a Product Description.  This will describe the general characteristics of the particular silicone, its category and type, and an idea of its texture, hardness, mix ratio and suggested applications.

Here are a couple of examples I randomly pulled out of my file (you should always keep this info for future reference): Continue reading

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The How and Why of Silicone. (Part 1)

Understanding Silicones: The uses of silicon in FX; Tin vs Platinum; Behaviours and Applications.

First point, for anyone who isnt sure, Silicone, the synthetic polymer, is correctly spelt with an ‘e’ on the end, to distinguish it from the metalloid element, Silicon. Technically, it is a misnomer anyway, that dates from their discovery in 1942, it was thought the structure of the compounds was similar to ketones, when they are in fact Siloxanes. However the name Silicone has become accepted and persists to this day.

Right, that’s out of the way, now to business…..

What is Silicone?

Here is the Wikipedia definition: http://en.wikipedia.org/wiki/Silicone
The Encyclopaedia Brittanica explanation: http://www.britannica.com/EBchecked/topic/544410/silicone

and for the real chemistry nuts, Dow Cornings spiel: http://www.dowcorning.com/content/discover/discoverchem/properties.aspx

Does any of that help? Well, maybe, but it wont necessarily help you make that mould/art piece/prosthetic or the like….

Basically, silicone, for our purposes, is a synthetic polymer, which sets, or vulcanizes, at room temperature, into a rubbery material. This is known as RTV Silcone. It comes in hard and soft formulations, is inert once cured, heat resistant, flexible (even in hard kinds) and very very useful! RTV silicone rubber is used in the movie, entertainment and special effects industry, and in theme parks. Soft “skin” silicone rubbers, used by make-up and Fx artists, were developed specifically for sfx makeup artists, and certain kinds are also used in the medical prosthetics industry. It is also used, in an uncured form, as a lubricant, which will be apparent to anyone who has ever spilt uncured silicone on their floor…. it is an immediate shortcut to the kind of slide action Tom Cruise was famous for in ‘Risky Business’…..

So how do you know what kind of silicone to use? That depends on what you are using it for…. First I will go through some basic information that everyone should know before they start. Continue reading


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