The main material is liquid latex, so a few words of warning before we begin.
Please use all normal safety procedures when handling materials and carrying out processes.
Some people have a natural allergy to latex, if they are over 16 years old they will normally be well aware of any such allergy, but please ALWAYS carry out a simple allergy test BEFORE you go playing with this stuff, or sticking it to anyone else!
Also, liquid latex smells like cats piss when it's wet. This is a very small percentage of ammonia that is added to stop the raw latex coagulating in the container. This smell will vanish once the latex cures, but people with very sensitive skin may find it an irritant when being stuck on.
It is advisable to work in a ventilated area.
Please take all precautions necessary.
However, in its natural state it is very heavy, and does not bulk out very easily. Therefore, most movie prosthetics are made from foamed latex and this presents loads of problems for the home movie maker. It needs foaming agents adding and then baking to cure ..... all too much hasstle for me.
In order to use it straight from the bottle, we need to embed stuff in it to bulk it up whilst keeping the weight down. We need to use theatrical grade latex which has a low ammonia content (do an ebay search there's loads of it on there). We also need to keep the final results soft and pliable (it's going on someone's skin after all).
There are many articles on the net about creating wounds and 'zombie skin' by adding oatmeal to the latex etc, these work well but I was looking foe something a little more dramatic.
Theatrical grade liquid latex
Greaseproof or wax paper
Cotton wool balls, pads rolls etc
Sponge rubber pipe lagging or stiff foam rubber
Water based paints (artists acrylic or acrylic ink, watercolour etc.)
Put simply we are going to encase the cotton and sponge in the latex in layers.
Lets begin with a rib cage.
Tape the wax paper down on your bench, draw the basic shape of the rib cage, then paint on three thin layers of liquid latex allowing each to dry in between. The layers are dry enough to work once they go from white liquid to transparent rubber.
Get your cotton wool balls and unroll them, it's easy to find the end and unroll them.
Pull the cotton out into the basic shape, dab a little latex down where the cotton will go then plonk the cotton down and push it into shape.
Coat the upper surface of the cotton with liquid latex, use plenty of latex and a dabbing motion so as not to pull the cotton back up. make sure you get a seal at the edges. Allow this coat to dry, add more cotton and repeat until you have three layers of latex above the cotton.