Building the Giant

[jafisto]

I am working on a sculpture of a 12 foot tall man, using many different materials. While I have to do be very resourceful on how to make certain things work, considering I am not exclusively a sculptor, but over all I have been able to make things work. Nothing really has gone wrong. But now I am at dilemma.
I am working on the first arm. I sculpted it out of Plastilina Clay with a wood and wire mesh armature underneath. The thing is size of a large man's leg, weighing 60+lbs. When I sculpt on it, I have it hanging from the ceiling by rope. I plan on using a silicone mold with a plaster shell on the outside. I am going to coat it with resin to make the final product. So anyways, question- How do I divide the hand and arm so I can remove and put the mold back together? It was suggested to me to the hand like a glove, but I don't know how to do a plaster shell, and if no plaster shell on the hand, how do I keep the hand-wrist connection together, and what about the rigidity of the silicone?
So basically, using silicone for the mold and plaster for pouring resin in, how do I divide the hand/arm up?

[fritchie]

Jafisto - First of all, welcome to the Community, as I see this is your first post. When I have done full human figures, I always have split the mold for the hand into front and back. In other words, run a cut around the longest edges, along the thumb and across finger tips to the little finger, then back to the wrist.

As the arm is more or less circular in cross-section, division there is less critical, just whatever is convenient and least likely to be noticeable.

Typically, a silicone mold will have a plaster mothermold to keep it rigid. Overall, then, you would have a two-part silicone mold, front and back of the hand and arm, and then a two-part plaster mothermold over the two silicone parts. You should have alignment cuts or groves in both the silicone and the plaster mothermold for correct alignment.

[sculptor]

My normal aproach is to use a resin/fiberglass mothermold for life and larger pieces. It's lighter, stronger, and offers some flexability for demolding with slight undercuts.
Then, I try to have as few continuous segmentations as posible----none is the prefered.
I prefer to split the arm mold along the length of the arm with a jog at the more cylindrical cross section at the forearm.
so, I'd make the arm to hand piece continuous on the inside of the curve, and seperate the outer shell at or just above the wrist----this means that the hand needs be a tad thicker than on a real person-----no one has ever noticed this.----but if you examine the mermaid's hands closely, then compare to your average woman---even an athlete--you will see a varience of perhaps 20% to the upside at the wrist to palm connection

I'd eschew the "glove" approach
It has been my experience that even when I was able to remove the mold without tearing it, casting within this blind alley was an unworkable solution

if you'll post a picture of your clay, then we could offer some more detailed and directed avdice.

either way, experimentation will guide you to your own approach.

best wishes and welcome

rod
sculptor