silicone softness

Well aren't I just the silliest of sillies.  Dory left me a lovely comment following my last blog and I thought I was responding to Dory but it turned out I was actually deleting my blog piece.  Not to worry, it wasn't exactly a literary masterpiece.
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Anyway!  Today I wanted to start talking about silicone softness.

There are two types of silicone used to make dolls, platinum silicone and tin silicone.  Tin silicone generally comes as a pourable silicone and a liquid catalyst which is mixed with the silicone.  The catalyst makes the silicone cure, generally tin silicone is poorer quality, doesnt come in the lovely super soft softnesses, and it breaks down much quicker than platinum silicone and being harder it tears easily.  So we are not going to talk about tin silicone.

So platinum silicone is the stuff they make medical prosthetics from, it is super soft, very stable and lasts a lifetime.

Platinum silicone we use for making silicone babies is so soft it comes with its own scale of softness, the 00 scale.

Okay so I might have just made that up - the bit about platinum  having its own scale of hardness.  But it is super super soft and wonderful quality.

So there are three hardness scales when it comes to measuring any rubber (silicone rubber IS classed as a rubber, similar to latex rubber, it is referred to as silicone rubber).  The A scale is the general scale for measuring rubber softness. 

As you can see from the scale, a pencil eraser is a Shore Hardness of A40.  If you look up at the top '00' scale, you can see that a Shore Hardness of A40 is approximately the same as a Shore Hardness of 00-78.  That is quite hard.

The silicones we use for making and painting our babies are on the 00 scale.  However, some of the mould making silicones are harder and are measured on the A scale.  Therefore you have to be careful to check when choosing silicone, how hard the silicone is.

Ecoflex 20 is measured on the soft 00 scale, and is 00-20.  Ecoflex 30 is 00-30.  Ecoflex 10 is 00-10.  You get the idea.  Ecoflex is a soft platinum silicone.   

Now ... Platsil Gel 00 is measured on the softer 00 scale (the name is a giveaway) so when I talk about using Platsil for fixing and painting babies, I am talking about Platsil Gel 00.  This has a softness of 00-30 and can be used for pouring babies, it is excellent quality just like Ecoflex.

However ... Platsil Gel 10 many would assume has a softness of 00-10 but it does NOT.  Platsil 10 is measured on the A hardness scale, and has a hardness of A10 (around 00-55).  You really don't want to pour a baby with a Shore Hardness of A10.   

So the difference between Platsil Gel 00 and Platsil Gel 10 is IMMENSE.  

I will talk again about silicone softnesses and properties, the viscosity, cure time etc, but a little at a time, the thing is to ALWAYS read the technical data sheet when using a new product.  Don't even buy it until you have studied the technical data sheet, study it and understand it. 

This is a section from a technical data sheet for platsil.  You can download the technical data sheets off the suppliers websites.  They are fascinating, and they tell you everything you will ever want to know about how the product you are buying will handle, how thick it is for pouring, how much time you have before it starts to 'gel', and how soft the silicone will be when it's cured.

Another time I will talk about various other things to do with silicones but for now remember the Shore Hardness Scale.  So many times people ask me "is Dragonskin 10 the same softness as Ecoflex 10?"  The answer of course is NO.  But everybody can find out that for themselves by simply checking the Short Hardness of the silicone.