Foaming the arms and legs

So Easter holidays are over and I have access to the workshop again. I used Mould Foam 8 (R8) polyurethane expanding foam to fill the arm and leg moulds. The arms are actually surprisingly thin and only took about 400g each (with lots of excess). First pic shows how I will suspend the solid box section I milled down to fit inside some hollow box section (set aside for later), in the moulds so they'll be securely imbedded onto the arms after demoulding. Second pic shows part A ready to be poured into a bowl of part B - mixed quickly with a big disposable brush. Third pic shows the other arm mould after the foam has finished expanding and has totally cured.

The legs are a little bit more complex so I'll let the photos make sense of it - I temporarily taped the metal plate (that I made to sit embedded in the Kijimuna's bottom) onto the solid box section protruding from the inside of the torso's core (I put the torso back into it's mould for this whole process)). I then sealed the torso core from the leg/bottom cavity with several layers of polythene sheet - this is to stop the foam from expanding into the torso core (I want these parts to remain separate so they can be detachable for transportation purposes). I poured one leg at a time until there was only the bottom section not filed with foam. I then bolted the sealed off torso mould onto the legs and poured the rest of the foam through a hole at the bottom of the leg mould (I obviously cut away the flap of silicone that originally covered the fiberglass section I cut out).

You can see that the metal plate is now hiding inside the bottom and the torso will now locate perfectly onto the legs every time (hopefully!)

Casting Issues / Repairing the arms

So after a successful demould of the head and torso - I have come across a BIG problem when attempting to demould the arms. Most (if not all) silicones are known for not sticking to anything but themselves... and (unless casting silicone into silicone) release agents are not essential at all.

I covered my moulds in a light dusting of Macwax - a very common spray release agent that works well with Platgel pieces and many other materials. Despite this, I realised I was having problems getting the parts of the arm moulds off the cast because the Platgel had CHEMICALLY BONDED to the fiberglass. There is normally resistance when demoulding because of the suction created by the silicone - once the air creeps it's way back between the mould and cast, the mould parts eventually come away fairly easily. My arm moulds have no undercuts or heavy texture so there is no chance of this simply being a mechanical bond. The moulds were clean, dry (before the macwax was sprayed) and loosely covered with clingfilm to prevent dust n bits falling in - because of this I am confident that the gelcoat was normal and prepared properly for casting.

I realized the Platgel had bonded when I had been slowly knocking wedges all the way round the flanges, instead of new parts of the Platgel's surface becoming visible as the gap got bigger - it was the same area of silicone stretched between the two flanges. I attempted to pull the silicone away from the inside of the mould and was successful but it was incredibly stuck on there! Suction does not do this, it wouldn't do this even if I hadn't waxed the moulds.

I submitted my problem to a large community of industry professionals and hobbyists on Neill Gorton's Make-Up Effects 911 facebook group. This is exactly the kind of thing that they encourage people to post - so everyone can benefit from other people's experiences...

I had '0' explanations to my casting issues - go figure!


After eventually getting the first arm demoulded - I decided to slice the skin of the other arm as close to the existing seam line as possible in order to get the mould open enough to be able to grab the silicone and pull it away from the mould with force. I would then have to glue the silicone back onto the expanding foam core.


Here are a few hideous pictures of the damage caused:
I didn't take that many cos it is, quite frankly, embarrassing....

The damage on the first arm from the silicone being peeled off the mould looks like someone's dragged a disposable shaver over the surface (first pic). I will have to cover this in the seaming process as well...

Here are some snaps of me attempting to repair the right arm (the worst one). I used clear RTV bathroom sealant to glue the majority of the silicone back into the foam. I then used a fast setting silicone adhesive called ELASTOSIL A07, to glue the meeting edges together as neatly as possible. I will potentially have two seam lines to cover after I've finished...

Casting the arms and legs

Unlike the head and torso, the silicone will be brushed in the arms and legs and then filled with rigid expanding foam. Here's a photo of the leg mould sections after the silicone had been applied. I imbedded strips of material into the surface of the thickened layer of silicone so this will bond to the foam.

I did the same for the arm moulds apart from also adding in a piece of thick armature wire, also wrapped in material, attached to some thinner armature wire for each finger. These wires fitted into the channels in the moulds' flanges. I also placed these thin wires into the toes of the feet as well before attaching them to the leg mould. This will mean I'll be able to adjust the position of the fingers/toes, it will also make them easier to paint evenly.

I have to wait until I have access to the workshop at uni in order to cast the foam into these moulds - I'm only able to do small urethane castings in my kitchen because of the lack of extraction!

Casting the head and torso

Today I began casting out the head and torso. I made a GRP core for this section a couple of weeks ago so I will be pouring my Platgel 10 into the cavity via a pour tube. Normally the pour tube would be attached into the core so there wouldn't be any excess silicone visible on the outside (visible) part of the cast. But in this case, I'll be taking advantage of the round hole made in my outer mould from the scaffolding pole that was holding the sculpt up on the table (see previous posts on the armature and sculpting processes).

The excess silicone left in the pour tube will be trimmed back, disguised during the seaming process and eventually covered in hair.

After drilling some bleeders to allow air to escape from the cavity, I filled each ear with silicone and let them totally cure before putting the core and mould together. This was just to make sure the ears filled properly - because of their complex shape, there was lots of areas for the air to get trapped if they had been filled up at the same time as the rest of the cast.

This image was taken just after I'd finished pouring the silicone. You can see how the Platgel has made it to all of the bleed holes and the next image shows air bubbles in the silicone rising out of the bleeders as well.

After the silicone was fully cured (checking the state of the exposed Platgel in the funnel), the funnel and tube was removed, the excess silicone was cut down to ease de-moulding. I decided to de-mould the face first - because of the slight translucency of the GRP mould, it's possible to see the pinkiness of the Platgel from the outside. This was useful when pouring the silicone because I could see where it was travelling through and filling the mould. I made sure to take the screws out of the eye blanks and teeth unit so they didn't get yanked out of the face when de-moulding - they might've actually stopped me from being able to take the mould off the face.

The chest and neck piece of the mould was the last piece to remove but because of the vacuum created by the silicone I had to split the Platgel skin up the back with a scalpel and use the core to push the chest piece away. This is why I created keys in the core so if I needed to do this, the silicone skin could locate back onto the core perfectly. Here are images of the head and torso straight out the mould...

Translucency and flocking tests

I want to make sure my silicone is as much like real skin as possible so when it comes to painting it I already have a really good base tone and translucency. I also had access to several different shades of flock. Normally it is only necessary to have red, blue and yellow shades to create different variations and out of the samples I found in the studio, I only ended up using the short strand red flock to get the desired shade.
Here's my silicone test tiles (cast from an existing fastcast mould of some skin texture). From L to R: over-exaggerated red tone, light flock density, heavy flock density, under pigmented sample, first pigment test of A+B batch, second pigment test of A+B batch after changes.

The bottom right sample is the translucency that I went with in the end - I used a black spot drawn on a tongue depressor to test how translucent the silicone is compared to actual skin. A consistently effective method practiced by Neill Gorton. I added a medium dense mix of red flock which warmed up the tone some more. I'm happy with how it looks on the depressor and in the bucket so I'm now ready to start casting out parts...

Coring out

I decided to just core out the head and torso section of this mould due to the time restrictions of the workshop and to help stay on schedule before the Easter break. The silicone in the legs/feet section and the arms will be brushed in and then filled with rigid expanding foam (R8/Mould Foam 8). These photos show the even layer of clay I placed into each section of the mould - less than 10mm - and me fibreglassing it in sections to ensure full coverage and less clean-up time.

 

  

I put clay squares into the back so the silicone would have keys that located into the core in case I ever need to take the skin off for punching the hair etc...

De-moulding

De-moulding pics are pretty boring but here's one called 'the aftermath'. I kept the eyes blanks and teeth unit and screwed them back into the front of the mould ready for coring out tomorrow. I won't be cleaning the torso out just yet as I'll be putting clay back into it soon anyway.

Trim time

So today my mould was hoisted back down to the ground floor of the workshop and wheeled to the sanding room for trimming. This is the biggest, most complex mould I've done so far, so I found it more tricky to cut down in some places but it's great to see it looking less lethal! Here's a snap of one of the arms being trimmed, and one of the body, arms and feet all neatened up...

Moulding wk2

Restricted to the opening hours of the workshop, I'm finding the moulding process is taking a lot longer than originally planned. I finished all the external parts of the mould yesterday, here's a collection of photos from this week showing the rest of the process.

The photo above shows the left arm with the bolt holes drilled. I tried to drill and bolt as much of the mould as possible whilst waiting for other parts of the mould to cure etc. The picture below shows the mould with all the holes drilled and the bolts taken out ready for de-moulding of the original sculpt along with a close-up of the screws that I drilled into the eye blanks and teeth unit...

Moulding wk1

Yesterday afternoon I used brass shim to section off the top part of the left leg ready for moulding. The plan is to start at the bottom and work my way up the front until the neck is fully supported by the fibreglass. This means I'll be able to cut the support wire at the back of the head and clean this up before moulding that section. Hopefully the photos explain the order of things...

Most sections are big and simple enough to be walled up with the shim but the hands and feet will need to be clay walled. Also, for the time being, I'll be keeping the removable platform in place to help the scaff. pole support the sculpture during the majority of the moulding. Then I'll take it away to glass the underside...

Hoisting day!

I nervously took photos of my sculpt (w/o the arms) being hoisted up the side of the workshop - the resin room is on the first floor and it was definitely too heavy to carry up the spiral staircase. The awkward look on his face is quite fitting for this situation!

It was then lifted onto a low trolley and wheeled round to the resin room. Here's some photos I took just before I started moulding...