Face casting is the first step to producing a positive replica of your models face. The face casting, which is usually done with silicone or alginate, produces a negative of the person's face, which is then normally filled with plaster. It can then be sculpted on to produce prosthetics. 

Silicone

is obviously more expensive, but can take a more accurate impression and pick up more detailing. This is because the silicone 'grabs' the skin a lot more, which can be counterracted by adding a rich moisturising cream all over the skin and bald cap. Just as with alginate, scim can be added to the silicone before it sets to add strength and aid adhesion to the plaster bandages.  Because the aplication of silicone is thinner than alginate, there is less cushioning between the model's skin and the plaster bandage casing. Therefore extra care must be taken when removing the cast to ensure the model's skin is not bruised. Another advantage is that it you can reuse a silicone mould repeatedly and it will not shrink or distort over time. You can also make an immediate fibre glass positive to sculpt on which you can't do with alginate. Silicone also has less lumps. 

Alginate

is a powder derived from seaweed that becomes a paste when mixed with water. It is also used by dentists for taking teeth impressions. It is temperature sensitive, meaning the temperature of the water will determine how fast the alginate sets. The consistnecy of the paste depends on how much water is added to the powder. Many types of alginate are available. Several manufacturers make 'prosthetic garde alginates' that provide a good working times even when used with tepid water, which is more pleasant for the model. 

Plaster bandages

As alginate is flexible, you will need to reinforce it with plaster bandages to provide support. Plaster bandages are rolls of gauze saturated with 'plaster of Paris', which are dipped in warm water, squeezed out and applied to the alginate, setting hard in about 10 minutes. 

Scrim (burlap)

A light, open texture material usually made of cotton or flax, scrim is used to add strength to and reinforce the mould to prevent rcracks from appearing. The scrim is cut into small squares, (depending on the mould). 

Low-expansion plaster

As they set, all plasters expand to some degree. However, a low-expansion plaster is best as it expands less, and is unlikely to crack. 

 

 

 

The Process

- Always have atleast 2 people working on a life cast so someone can keep an eye on the model's nose for breathing.

- Cover any hair with vaseline. If you are doing a full head cast, a bald cap will need to be applied to the model ( a cheap latex one will suffice. Once it is fitted, take a water-soluble pen and draw in the models hairline. This will trasfer onto the alginate, which can act as a helpful guide when sculpting. Cover any eyebrows and eyelashes and use a thick layer if covering any facial hair.

- Prepare the alginate for use; two cups of alginate and two cups of cold water. When you are ready, mix and start working immediately. Alginate doesn't stick to dry alginate, so when the mixture dries up then you can no longer apply the mix.

- Start application to the forehead. Constantly talk to your model, telling them what is happening, where you are putting the alginate, are they ok, etc. Push the alginate up into the inner corners of the eyes and over the eyelids. This is one area reffered to as an undercut, which can be prone to trapping air bubbles. 

- Keep a good thickness - anything less than 1cm is too thin. 

- Cover the whole face, leaving the nose until last. Use a spatula to work around the nostrils. 

- Once the face is covered can be pressed into the wet alginate on the forehead and chin areas. This will ensure the plaster bandages adhere to the alginate and do not seperate from it when removed from the model. 

- The plaster bandage is then applied to the alginate. This is used as alginate is too floppy to make a mould from. Its needs to overlap in order to stick to itself. One long piece should be applied around the outside for support. The nose is left so that it can be bandaged later, otherwise it can be distorted. This sets within about 10 minutes.

- When set, ask the model to hold the front sides of the mould, lean their head forwards and wiggle their face so the mould slowly eases away from their skin. 

-When the cast has been removed it should be positioned in a bowl so that the nose is not leaning against anything. Plaster can then be applied over the nose and damp couchroll should be laid over the mould and put up the nostrils of the mould to stop it drying out or distorting.

- The mould is then ready to be filled with plaster or other medium

 

 

Conway, J. (2004) Makeup Artistry for Professional Qualifications. Essex: Heinemann. pages 358 - 362