Full Head Casting: Take 2

Today I re-attempted to cast a full head. I bought a higher quality alginate and bald cap. I also employed the assistance of a friend with casting experience to help me work a little faster for the sake of my model.

I started by making up a small sample of the alginate, because the container said that you only needed to cover hair with a release agent, that it would not stick to other surfaces. So I put a small sample on the bald cap, and indeed, it peeled right off.

I attached the bald cap with spirit gum and applied vaseline to the model's exposed hair (sideburns, eyebrows, eyelashes). I then had him insert his own breathing straws for comfort.

 I then mixed the alginate with an electric mixer to speed the process. The alginate was supposed to be mixed at a 1:1 ratio, but I reduced the water a little to get a thicker consistency so that it would not run down the face as much. Based on my first attempt (see earlier post), I used a bottled water to mix the alginate because the tap water here is unsuitable.

We began applying the alginate starting with the undercut parts of the face: chin, mouth/nose, eyes, ears. After those sections were covered we began dumping the remaining alginate over his head, allowing it to run down over the features. We had to be constantly vigilant about the alginate under the chin and ears because it kept running down the neck.

 As soon as the alginate was on, and before it was set, I added small pieces of terrycloth to the front half to help the plaster bandages stick to the alginate. We gave the alginate about 10 extra minutes to fully set. We then began applying the plaster bandages across the front half of the head to create a hard shell to support the alginate. I added three 'keys' in the bandages to allow the front and back to have a perfect fit when we realigned them. We built up the wall around the edge of the bandages for extra support at the meeting point.

 After allowing the plaster time to dry, I applied a layer of vaseline along the meeting edge and keys so that the back half could be laid down right against the front and not stick. Once the two halves were together, we allowed them plenty of time to dry.

 To remove the cast, I carefully removed the back half of the plaster shell using a screwdriver to wedge apart any sticking plaster. Once the shell was off, I slowly cut a slit up the back of the alginate from the neck to the edge of the front shell. The model then leaned forward and slowly removed the shell and alginate together by wiggling his face until the alginate came loose as we helped pull the slit around his head. After the cast is off, I attempted to glue the slit back together with spirit gum (which was what my instructions indicated, but didn't work very well). To put the plaster shells back together, you spray the inside of the back shell with a spray adhesive, fit the two pieces back together, and tie/tape them. I found the tape did not work very well because the plaster was still damp.

 Once the shells were back together, i set up a box with packing peanuts and cloths to support the cast while the gypsum cement bust set up. Before pouring the cement, I noticed that the alginate was starting to leak water out and it was collecting the the crown of the head. I made sure to continuously soak it up so that a bubble of liquid did not form in the top of the bust.

Once the cast was set up and ready to go, I began mixing my gypsum cement. The package indicated a ratio of 38:100 water to cement. This makes a thin creamy substance, but beware, it will set faster than you think. I used a paint stick to help guide the cement into the head and to help prevent air bubbles. Using a ladle, I poured the cement down the stick to let it slowly fill the bottom of the head. As it rises it pushes the air out ahead of it. I gave the cast a couple of taps as the cement filled the nose and chin to help any bubbles come to the surface. The directions I had said to make the gypsum in two batches. I made the mistake of not having the second batch already measured, and the first batch was quickly setting Although it was still viscous enough when I began pouring the second batch, i made a couple of small indentations in the first to give the second a set of keys to stick in. Always be prepared with your next step.

Now I must wait 24 hours until removing the bust from its shell. Then it will need about a week to fully dry.