DIY Mold (Quick and Dirty - The Amateur Way hehe)

1. You'll need a robot head  
2. Epoxy Putty like this http://www.selleys.com.au/Selleys-KneadIt-Multipurpose/default.aspx or Tamiya etc.
3. Just cut a big piece of the putty and mix it until the color is uniform white/yellow (depends)
4. Take the head and put some liquid soap all over it
5. Press it against the putty (clay)
6. After a minute or once you feel the putty is hardening, try to pull out the head. If done correctly and patiently you'll get a mold of the head.
7. Cut another piece of the putty and mix it.
8. Take your new mold and fill it with soap again.
9. Press the new putty against the mold
10. When you feel the putty is hardening, slowly pull out the new puttty.
11. Trim excess and add/sculpt additional/new details
12. You will have a brand new head without spoiling the original  

I'll try to add in more details next time   Hope this would help others out there

NOTE: If your wondering why soap its to avoid the putty from sticking permanently to the original mold.

You can repeat the whole steps for the back of the head and put them together. But I normally just hand sculpt the back since I don't find it necessary specially for transformers.

Here are other heads I've done using this amateur technique  

Original mold from an ALT Sideswipe

Original mold from a Galaxy Force Megatron


Original mold from a KO DeathSaurus


Original mold from ALT Smokescreen


Original mold from Robot Replica Bumblebee


Handsculpted


Handsculpted