The first thing you will want to do is have a full head armature to sculpt your mask on. You can use either a lifecast of someone if you have one available or you can purchase a standard armature from a mask making supply site, I recommend www.monstermakers.com

Once you have the armature that you will be using, it is time to decide what clay to use, that is up to you. There are oil based clays like Roma and chavant that Never dry out and can be reused and there are waterbased clays that can in most cases be used only once. I like to use a Water based clay called WED clay or EM-217 by Laguna clay it is called WED since it was designed by Walter E. Disney for large scale sculptures for his theme park. It is very easy to work with and smooth with simple water. It stays easier to work with and dries out slower than other water based clays since one of the key ingredients in it is Glycerin.

Once you have the armature and the clay you will use it is time to apply the clay to the armature. You want to have atleast an 1.5 inch to 2 inch thickness since once you cast the sculpture in latex it will shrink 15-20% roughly. You will want to make it to go even thicker if you plan to make a one piece copy mold off of your latex master copy. Once the armature is clayed up to the desired thickness you will want to set in something for eyes you can use glass eyes or even marbles.

Once you have your eyes set rough out the rest of the head proportions, based on what ever character you are making. I always suggest roughing everything in before starting any detail, nothing is more frustrating to me then detailing an area then realizing the size or placement is off and then have to restart. Another tip is to step back from your sculpt from time to time so as not to get over focused on the small details only to realize a glaring mistake later when almost done.

This illustrates the placement of the mold wall and the way it should follow around the ear.

Before moving on to the next step you will want to have at least 50 LBS of ultracal or Hydrocal plaster, burlap and plenty of disposable chip brushes and a few old sponges. Once the sculpture is finished and the way you want it, right before molding you will want to seal it with a cap material such a krylon krystal clear. Give it 2-3 coats then hit it with a one coat of dulling spray. The Krystal clear will make it easier to remove the molding wall you will be adding next.

After the cap material is dry you will want to start making a dividing wall, preferable with a cheap water based clay. The dividing wall should be place right at the middle of the sculpture basically dividing it in half. Make sure if your character has human like ears that you follow the out side edge of the ear with the wall front half of the ear is part of the front half of the mold and the back of the ear is part of the back half of the mold. You will want the mold wall to come about 2-3 inches up from the sculpture and be at least 2 inches thick. I always suggest making the back half of the mold first.