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.



Moulding & Casting - Head

In this Post I'll be continuing the process of creating the head for the Actress (Elle) Puppet. In my previous post I completed the master sculpt of the head and facial masks. I will now be moulding those parts and casting out plastic copies.
You can see Josh's post about Moulding and Casting the Mail Man's heads HERE. I will be using the same process.
A general rule for mould making is -
When casting hard objects, a soft mould is needed. When casting soft objects, a hard mould is needed.

As my head sculpt is hard and I will be casting copies in solid plastic, I will be moulding the heads in soft silicone.

Firstly I decided where the 'pour spout' will be located. The pour spout is the cone shaped hole in the mould where the resin will poured in later. I start by making a small cone of baked sculpey and gluing it the the sculpture using a glue gun. The hot glue holds onto the sculpt securely but can be removed easily later without damaging the head. In the picture above you can see the pour spout located under the head. The second function of the pour spout is to suspend the sculpture up off the surface.

Locating where to put the spout is very important. When it is cut off later it might leave a visible mark. Therefore its best to put it somewhere where there's no detail and it won't be seen. I've chosen to put it on the top of the head where it will be covered by hair.

Another important consideration is air bubbles. If the spout is incorrectly placed then air can get trapped in the mould causing voids in the castings. If the pour spout is positioned in the 'highest point' then air will be able to flow out of the mould without getting trapped.

I built a box around the sculpture made from foam board. The sides are glued together with hot glue to create a water tight seal. I left a gap of about 1cm around the head so that the silicone mould will have sturdy sides.

The silicone I'm using is white in colour and cures in 24 hours with 5% catalyst. When mixing the two parts together small air bubbles are introduced. These annoying bubbles can cause problems later and without a vacuum chamber they are difficult to get rid of. My solution is to paint a layer of silicone onto the sculpture and let that set. This helps to capture all the details and reduces bubbles on the surface. I then top up the mould box with silicone. I pour it in a thin stream into a corner of the box (not directly onto the sculpt).

Using this method means any bubbles that are in the mould won't touch the surface of the sculpture and therefore shouldn't cause any problems.

Once them silicone has set I removed it from the foam board box. Using a scalpel I now have to remove the master sculpt from the silicone. I cut along the back edge in a zig zag pattern and then bend the mould open to remove the sculpt. Cutting only the back edge reduces the amount of visible seam lines on the castings. The zig zag pattern will help the mould line up when it closes back up. 

To cast the head I used Polyurethane (Fast Cast) Resin. This is a two part resin that mixes together in equal parts and cures in 30 mins. No mould release is needed. The resin is most fluid and viscous in the first minuet of mixing so I had to work fast and get the resin mixed and poured into the mould as quickly as I could. (There was no time to take a picture). I gently shake, rotate and tap the mould to coax any bubbles out. After about 3 minuets the resin starts to thicken up.

Above is my first casting next to the master sculpture. I cut the pour spout off the top of the head and lightly sanded away the seam line. The fast cast copy of the head is much lighter than the original. Weight is always an issue for stop motion puppets in the fight against gravity. Another positive is that  fast cast is much stronger than the sculpey original meaning it is much less likely to break during filming.

Above you can see that the silicone eye socket and eyes fit snugly into place, just as they did in the original head. I repeated this method to mould and cast the brow and mouth masks. I've cast 10 copies of the mouth and 3 brows that I will use to make all the different facial expressions required for the film.

The masks fit into place neatly but I will be adding a magnet system to hold them in place.

In by next post I will be doing more mould making, only this time they will be hard Polyurethane moulds for casting flexible silicone body parts.



Puppet Head Sculpt - Actress Part 2

Today's post is part 2 of the puppet head construction for 'Elle'. This is the part I really enjoy as it mostly consists of sculpting. Sculpting is a hobby of mine and you can see some of my work on my website Sculpt-Double.co.uk.

Tools

Above is a picture of the tools I use for sculpting. Firstly on the left are some different clays. Super Sculpey Firm is a grey polymer clay that can be baked hard in an oven. I use this most often and it's great for capturing detail. Next is Milliput epoxy putty. It comes in two parts and cures hard in about 5 hours when mixed together. I use this because its really strong and good for strengthening and sticking together armatures. The ball of grey clay is Plastiline. It's a non drying clay very similar to plasticine.

I've collected a lot of different tools for sculpting, but pictured above are the only four tools I ever seem to use. On the left is a scalpel used for cutting and carving the clay. Next is a playing dart without it's flight ( my favourite and most used tool). The tapered point works great for sculpting in details. The red plastic tool I use for roughing out shapes and smoothing surfaces. Finally the last tool is a pin with a home made Milliput handle. This is used for really small, fine details.

I wouldn't recommend spending lots of money on expensive sculpting tools. Often found items and home-made tools do the job. To smooth out clay I often just use my thumb and fine brushes but it requires a lot of time and patience.

Sculpting the face

In the picture above you can see I have roughed out the face onto the Milliput masks. For this I used Sculpey Firm. I've added features like the ears and nose and marked where the mouth will be.

In this profile shot you can see the seem lines where the different parts of the face will separate. Below are the two mask pieces away from the head core.

Above are all the different head components so far. Rather than sculpting multiple replacement mouths from scratch, I will be moulding and casting out copies of one mouth and sculpting alterations onto the casts. This way the shape of the nose and cheeks will stay consistent and only the mouth shapes and jaw will change.

The 'master' face above has no lips sculpted so that they can be added to the casts later. I have added a set of upper teeth because whenever they are visible they should stay constant in a fixed position.

At this point the head and masks have been baked hard. Above you can see the rough sculpt for her hair. This is made from Plastiline and slots onto the head with K&S. The hair (once finished) will be moulded and cast in silicone.

Because part of the hair covers the upper half of the face, the brow mask is reshaped to follow the hair line. This allows it to be removed from the face more easily.

Finally here is the finished (master) head sculpt ready to be moulded. My next post will show the molding and casting process.