Mould Making - Hands & Feet

Its time to start a Mould Making Marathon.
A lot of the characters in our film require flexible body parts. Our three main characters need silicone components including hands, feet, arms, legs, necks and even hair. That means a lot of rigid two part moulds need to be made, and the process of making them can be very delicate and time consuming.
The duty of moulding and casting all these parts has fallen to me (Josh craftily escaped).

I've spent nearly two weeks moulding and casting all the parts for the puppets. Its an exhausting process but the results are looking good. I'm going to spread the whole moulding and casting process over a few posts, starting with Hands and Feet.
In this post I will be moulding a pair of hands for the Theatre Usher and feet for the Mail Man.

You can see my earlier post about moulding the Mail Mans hands HERE and I'm using the same technique.

Theatre Usher Hands

Above you can see the Theatre Ushers hands that were sculpted by Josh. They were sculpted in Plastiline over the wire hand armature. These hands are chunkier and larger than the Mail Mans due to the Ushers larger size. You can see the characters design HERE.

A wall of terracotta clay is built up around the sculpt, half submerging the hands. The hard part is getting between each finger. It takes a lot of patience. I've used yellow Plasticine blocks to act as 'keys'. These tapered blocks will help the two halves of the mould line up and fit together.

A foam board box was built around the clay and hot glued together (making sure its water tight). I applied Vaseline to the inner edges of the box and sprayed 3 layers of wax release agent over the sculpt. Release agent stops the resin from sticking to the clay. Once that had set, I poured Polyurethane Resin into the box and used a brush to make sure no air bubbles stuck to the sculpture surface. I topped up the resin, filling the box up roughly 1cm above the hands.

 

After the resin had cured I removed the foamboard box and flipped everything over. The terracotta clay was peeled away leaving the sculpted hands half submerged in the resin. Any remaining clay was washed away with water and a soft brush.. Above you can see the hands in the resin. I added more plasticine to the mould surface leaving a 1cm gap around the sculpture. These will lower the contact surface area of the mould, making it easier to separate the two halves. A new foam board box was then built around the mould.

After spraying the surface with 3 more coats of wax release agent, I poured the second polyurethane half. It's very important to use release spray. If I didn't the two resin halves would fuse together trapping the sculpture inside.Once that had set I removed the mould from the box and gently pried the two halves apart. The plastiline sculpture was removed from the resin and the mould was cleaned with Turpentine. Turps melts away clays like plasticine and plastiline. I will explain more about that later when I post about casting.

Mail Man Feet.

As you can see above, Josh has sculpted a nice pair of shoes over the feet armatures I made earlier.

You can read Josh's post about sculpting the feet HERE

Choosing where the split line will be is an important part of mould making. A seam line will be visible on the silicone castings. These are found where the two halves of the mould meet. Its best to try and disguise them so they won't be visible, but its also important that the two halves of the mould are able to be separated. This means there can't be any large undercuts.

The split line for the feet is concealed along the sole of the shoe. As before the clay was surrounded by a foam board box and release agent was added.

Above you can see the mould ready for the second half of the resin to be poured.

The Polyurethane resin is mixed in equal parts. Once it has set it turns an ivory colour. The resin cures quite quickly but the the mould making process is still very lengthily.

These two moulds are the first of many. I will be posting more pictures of the mould making process and they were all made using this general technique. In my next post I will show the finished sculpture of the actresses body parts and the moulding process.