Paul,
(and Bob)
I'll break it down into sections.
Heat set clay and plastic figures
Fimo is a putty that is hardened application of heat, about 120 - 130 degrees from memory.
This type of putty is often baked in an oven.
It can also be boiled in water.
Paul, you are changing a injected moulded plastic figure. The melting point for plastic is close to the baking point of Fimo.
The others have noted that if you bake the putty in the oven on the plastic figure, the figure may start to melt. (Same thing can happen to changing cast metal figures)
A alternative is to boil the putty for a bit longer - suspend the figure in the pot rather then let sit on the bottom, as the hot metal pot may distort the figure if in direct contact (metal pot touching plastic figure)
Then you may convert a plastic figure with a heat set putty.
Recent thread on baking in the oven
http://www.planetfigure.com/forums/showthread.php?t=30085
Scorching
When baking a figure in an oven, parts of the figure may become 'overcooked' for a variety of reasons.
example. Some one once sculpted a figure of Yoda. Baked well, where the putty was thin (on the long narrow ears) there was some browning where the thin layer of putty was slightly overcooked. Rest of the figure was baked properly
These areas may be a bit more fragile, but you are going to paint it, aren't you
Armatures
Bob, you asked about armatures. Armatures help get the dimensions right of a figure (or a bust) at an early stage. Trust me, it is far easier to check a simple wire figure against references then it is to modify a figure full of putty.
Once the armature is done, it usually bulked out with something like aluminium foil (for example) to give something for the putty to grab onto. Wrapping the armature with wire gives grip, as putty can slide off smooth wire.
Then you work out from those layers as you go.
Hope this helps.
cheers
