Mould-making and sculpting masterclass
Posted by Martin on November 16, 2009
I spent most of this last weekend at Calpe Towers as Peter F’s guest. It was the long-planned opportunity for me to learn the basics of mould making and pick up some sculpting tips in readiness for my forthcoming venture into Frankenstien monster-like conversions of some Calpe Saxons. We covered so much ground that it’s hsrd to know where to start. So let’s just dive in.
On the Saturday, Peter demonstrated the art of mould making. The creation of a successful mould is indeed an art. Anybody can make a mould but it takes considerable skill and thought to make a mould that captures all the detail of the master figures and can survive repeated use without degradation or damage. I’ve learnt that the orientation of the figures in the mould, the way they’re sculpted in first place, the type of rubber, temperature, pressure and the duration of “cooking” time all make a contribution to the quality of the result. Even how you pre-warm the rubber beforehand makes a difference.
On top of all that, you need a bit of physics knowledge to understand how the forces affect the flow of molten metal into the mould while its in the spin casting machine. Plus, you need to bear in mind that the air displaced from the mould cavities by the metal needs somewhere to go otherwise you end up with trapped air bubbles. Hence the need to cut and drill vent holes in the mould after its been made.
While waiting for the mould to “cook” we started on my sculpting tutorial. Rather than actually embarrass myself, I was content to watch Peter work and listen to him as he described the tools and techniques he uses. He also took the time to explain how he designs figures carefully with minimum risk of gaps and unsupported parts that would result in easily torn rubber in the moulds. Peter also showed me the ingredients and proportions he uses for his mixture of sculpting putty and I ended up mixing up several batches as work progressed on several figures over the weekend. Mostly we focussed on an NCO for the new set of Saxon line grenadiers but we also did some work on some greatcoat wearing figures that will emerge in an exciting release some time next year (once some minor problems with production mould quality have been resolved).
In particular I learnt how to get a smooth surface finish on putty, add fine details of various sorts, add buttons, make shoulder swallows for musicians, create wire armatures for limbs and bulk them out with putty, create folds in clothing and make blanket rolls worn bandolier style. Phew, what a lot to absorb! Now I’ve got to go away and practice. If I do a good enough job, Peter’s offered to make up a mould so that I can cast off a few of my own diabolical creations. No pressure there then 🙂
The other job we managed to get done was a short photography session (you can see a glimpse of the output above) and hopefully some of the other shots will be of good enough quality to be used by Dan with my Wargames Illustrated Prussian article. If so, I hope that the article will appear in the next issue.