Closed Mold Making

A closed mold is the way to make a prosthetic piece that fits the models face perfectly and can be made on noses etc. which would be impossible to sculpt from a flat piece. You start off by sculpting the piece onto a face cast of your model with clay. Then add grounding around the piece.

Grounding is a rectangle shape of clay that goes all around the piece. It follows the shape of the sculpt always staying about 5mm away from the edge of the piece. It is used to give a very thin edge to the prosthetic and it squeezes any excess material out of the mold. Due to this is needs neat even edges so edges need to be trimmed so they are sharp. 

The grounding then has touch downs inside it. Touch downs are holes that go through the grounding and several are needed all the way round the piece. They make sure that the top half of the mold locks down onto the bottom and doesn't move or slide around. 

The grounding then needs channels coming out of the piece so that the prosthesis material can flow out of the piece when the two halves are put together. A wall can then be built around the grouding to keep the plaster in place but it isn't completely necessary.

After piece is sculpted it needs to be covered in plaster. The plaster needs to just go over piece and be built in a square not round shape. It needs to be the same height all the way over and have a flat a top as possible. When the plaster is dry the two halves have to be separated and the clay cleaned out completely. Then to make the piece the prosthetic material needs to be put in - either melted gelatin, 5 layers of cap plastic followed by silicone, or latex. The two halves then needs to be pushed together so that the excess material flows out. Then the piece has to stay together whilst the material dries and can be separated when it's set and taken out of the mold. 

Example closed mold

Basic face cast to practice on

Practice nose tip with Anne Boleyn portrait in mind (nose is normal looking but slightly elongated)

Grounding, touch downs and channels on piece

I moved the grounding closer to the piece so it's 5mm away the whole time.

First try at a gelatin piece - has rips round the nose due to cuts in face cast made when moving grounding.

Evaluation

I feel that this first attempt at a closed mold did not go well. As the piece was on a generic face it was difficult to recreate the shape of what I want Anne Boleyn's nose to be like. Also due to the fact I had to move the grounding it created cuts in the plaster which when I tried to take the gelatin piece out ripped the piece. I attempted the nose 4 times and each time I continued to rip. I also think my touch downs were too small and need to be the size of a 5 pence. The grounding could also have been flatter and neater. Next time I do a closed mold I will try not make cuts in the plaster and do my grounding and touch downs a lot neater as although the nose tip could have been good it was unusable because of my grounding work.