Saturday, 1 April 2017

Getting a-Head

There are rather a large number of tasks required when building a stop motion puppet. There are also a variety of options to choose from in your construction. To save time and because at this stage of my project these are test puppets I would like to use the same head (and hands) I'm sculpting for my maquette for my finished puppet. To do this I need the exact same skull inside the head so I can cast the head in silicone several times and will have several inside components for it that will all fit perfectly (and one to stay in side the maquette). The ways I plan to try are:-

  • Dragonskin silicone
  • clear smooth-on silicone such as platsil gel 10
  • clear silicone with 'deadener' added to make it softer / more flexible
  • addition of pigment tests to make it flesh coloured
  • liquid latex
  • and possibly more than one lost wax style casting with with liquid chavant clay. 

Also, the head is going to have a relative thin 'skin' of silicone which means the skull has to lay exactly centred within it. This might be difficult to achieve so having more than one skull allows for some testing without having to destroy each test piece to get the skull out.

To have a skull for inside the head of the final puppet I have to consider:-

  • which type of armature I'm using and how the skull will fit onto the neck, ie will it be on a bit of square K&S brass tubing, a thick piece of armature wire, round brass tubing, on a ball from a ball and socket joint that screws onto a bit of threaded bar or some other fitting
  • what will allow me to fix the skull both to the animation armature but also to the neck of the maquette
  • what I will model the head on (as this is going to be sculpted separately to the body
  • how far down the neck sculpting will come to meet the body

The skull is made of Aves epoxy resin (similar to milliput) so is very hard, so I need a soft mould to cast the skull itself. I will make a one part mould for the skull in RTV silicone and then cast the skull in solid fast cast resin. Each skull will have a bottom jaw wire fixed to it but this will not be part of the cast though the holes for this will be. The eyeballs will be removed so these can be added separately later inside silicone eyelids to keep them in but allow them to move. 

As an aside the hands only have a wire armature inside them so no casting of internal structure copies will be used for them but they are relatively simple to make copies of as long as they always measure up exactly to the skeleton hand reference picture. Hands tend to break a lot in animation both because of how much they are used and because of having such thin armature wire inside so it pays to make several copies anyway. Also as the hand armature has to be placed exactly centred in the hand in very thin silicone cast this can need more than one attempt to get a perfect cast.

So the plan of action to make the head will be:-

  1. Make some eyeballs 4-5mm in diameter out of balls of baked sculpey or Aves epoxy resin. Using 1:6 scale human eyeballs should be around 4mm in diameter and aren't totally spherical but for this a little larger will help to make the eyes easier to work with and shouldn't look out of place as most of the eyeball is inside the head.I've used a micrometer to check both eyeballs are the same diameter (see previous post)
  2. sculpt an approximation of the skull in Aves epoxy resin, and leave overnight to harden. This doesn't need to be a beautifully sculpted skull, it just has to be smaller than the head itself in every direction, be roughly skull shaped and have eye sockets matching the eyeball size in step 1. I have added rough teeth for the top jaw for this as in StopMoNicks silicone puppet tutorial.
  3. Drill holes in the skull for the jaw wire using the correct size drill bit. drill a small hole for armature wire for neck. This can then always be drilled wider if brass tubing is used on the cast resin skull versions. Araldite (epoxy glue) the neck wire (make it longer than needed) into the base of the skull and put a loop in the wire end with pliers
  4. Make a mould box for the silicone mould out of foam board and glue gun. grease the mould box with Vaseline to help the silicone removal
  5. dangle the skull on its neck wire over the mould box on a cocktail stick or skewer. make notches in the mould box to hold it steady, marking on the box where the back of the skull will be.
  6. Make the silicone one part mould for the skull, leave it overnight
  7. demould the skull using a scalpel to cut a zigzag line on the side the back of the skull is facing and peeling it open. Remove the skull.
  8. Cast the skull several times in fast cast resin.
  9. Add jaw wires of two strands 1.6mm armature wire twisted together, make sure the same length is always used and glue in with epoxy glue (araldite)

When I have several skulls ready I will make a small shape of thick mdf about 6cm wide and drill a hole in this to insert the neck, gluing the neck wire and skull into this to act as  sculpting stand. This will also act as a holder when the head is cast. I will then glue on the eyeballs and bottom jaw wire.

Once I have a skull fitted with eyeballs, jaw wire, neck wire and fitted onto a small sculpting stand I will sculpt the head in Chavant Clayette Firm. This is a non drying oil based clay which is good at holding fine details.It is also non sulpher so will not affect curing of silicone used.

I will also make a mirror surround for sculpting the head out of three square mirror tiles and more MDF.

Once the head is sculpted in Chavant I will make a two part mould using water based clay (potters clay) and Jesmonite (a plaster resin mix) and then cast the head in silicone as above. 

The hands will be sculpted in Chavant, moulded in Jesmonite in two part moulds and cast in silicone with the armature inside. 

The ball and socket armature will be put together, covered in shrink plastic tubing, then covered in wadding and nylon to make a soft body.

Then I will repeat the process for the Lulu character possibly casting the whole body in silicone.

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