Green stuff moulding is a very easy and basic way to copy bits of models, conversions or parts of toys and other items that might suit your latest creation.
For example you might be creating a new space marine chapter for which you have sculpted a nice new chapter icon, instead of having to re-sculpt the icon for each model you can create a mould of the original work.
Before you begin you will need some well mixed green stuff, some Vaseline and the item you want to copy.
Creating the Mould
Step 1:
Place a little Vaseline on the area of the item you want to copy, this will stop the green stuff sticking to the model.
Step 2:
Press the mixed green stuff onto the surface of the model with the Vaseline on. Wait for the green stuff to harden.
Step 3:
Once the green stuff has set you can remove the original item from the mould.
Using the Mould
Step 1:
Apply some Vaseline to the mould and mix up some green stuff.
Step 2:
Press the mixed green stuff into the mould.
Step 3:
Let the green stuff harden then remove it from the mould. You may need to trim the finished item with knife.
Example
Below are some pictures of a skull I sculpted to look similar to some of the skulls you find on Space Wolf models. I needed several for a conversion and used the above process to create them.
The above picture is of the finished mould after the original sculpt was removed.

This picture is of a skull that have been removed from the green stuff mould before being trimmed.

A finished skull after the extra green stuff have been trimmed of.
Final Notes
The process it self is quite easy, one thing to note is that you will have to wash the Vaseline off before sticking the finished piece to your model and painting.
Other water based lubricants can be used instead of Vaseline.




