Before making a mold, you need something to make a mold of, namely a model. I am not going to go into sculpting in any great detail. Anyone with the ability and patience to paint miniature figures should be able to handle simple sculpting. I will offer a few pointers.
You need not go out spend a small fortune on tools. Such common items as sewing machine needles, pins, small screwdrivers, and hobby knives are all very useful. A particularly handy tool you might want to buy is a jeweler's burnishing tool. Not only is it good for sculpting, it is also useful for finish work on castings.
Model can be fashioned out of virtually anything. Bits of plastic, nails, screws, watch parts, and wire are all possible components for creating a desired shape. Start a "junk" box and save odd shapes for future use.
Epoxy ribbon is a good medium for sculpting. It is found in hardware and automotive parts stores as a blue and yellow strip. Cut off equal amounts of each color and knead until the new color is a uniform green, It can then be worked into the desired shape using small tools. It will have a tendency to stick to your tools. Dipping them in water occasionally is necessary. The epoxy hardens in a day and can then be filed, drilled, or cut as desired.
Adding details to a basic shape is easily accomplished with epoxy, To make a tank turret for example start with a slotted screw head and a small paneling nail. Use some epoxy ribbon to glue the nail in the slot, then add the smaller details on the nail "gun barrel" plus hatches, etc.
Figure sculpting can be handled in much the same way. Begin by making a wire "skeleton" and position the arms and legs or other appendages. Now apply layers of epoxy a little bit at a time.
Keep your first models simple. Avoid pronounced undercuts and complex designs until you are comfortable in your mold-making skills. Some models may be impossible to cast "as is" and will have to be cast in two or more pieces. Only through experience will you know what will cast and what will not.
It is important that you put the best possible finish on the model now. Molding rubber will not only pick up the nice details, it will also pick up every little imperfection.
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