On to part two:
Once you have a pretty good shape sculpted for your mask in clay, you’ll want to cover the clay in tinfoil. This allows you to smooth out the surface, refine details, and allows for easier excavation once it comes time to finish the mask. Slightly crumple a large sheet of tin foil and press it down covering the entire surface of your mask. Use your sculpting tools to smooth out the bumps in the foil and to add stronger details. If a few spots of clay show through the foil it won't be the end of the world - just remember that the more you cover the easier it will be to remove the papier mache when it is dry.
Next you need to prepare the papier mache. This step is twofold. First, you'll want to prepare the paper bags. You can also use newspaper, but when making masks I prefer to use brown paper bags because they are stronger, require fewer layers, and generally are faster to apply. To make the bags easier to work with, I crumple them significantly. The point here is to start to break down the fibers of the bags so that they absorb more of the papier mache mixture and to make the bags more flexible so that they are able to fold around the shape of your mask. The image to the right shows three paper bags crumpled to varying degrees. Ideally, you want your bags to look like the last one on the far right - like an old map or a worn piece of fabric.
Now you're going to mix the papier mache glue mixture. I use about two or three large scoops of wheat paste with a few cups of warm water and then add wood glue until the mixture becomes the consistency of runny snot. When your mixture is ready you can start to cover the mask.
Make sure that you spray the foil covered surface with cooking spray before adding any of the papier mache -
otherwise you will not be able to remove the mask. Allow each piece of bag to soak in the glue mixture for about 30 seconds to one minute and wring out the excess glue before putting it on the sculpted form.
I try to use at least three layers of bags, sometimes a few more depending on the mask, before letting the mask dry. As the glue dries I like to refine the details even more (this is especially necessary if your mask has creases because the bags will pull away and flatten out as they dry - try and monitor the mask every few hours). The papier mache should take two to three days to dry completely though the outside should be dry overnight. However, even if the outside is completely dry, it does not mean that the inside will be too. I've had a few occasions when I've removed the mask too soon and it's shape will warp because the inside won't have anything to dry against. It is better to be safe here and wait a little longer.
Next up:
Removing the mask and adding finishing touches
You should be able to grab hold of the newspaper ball and just pull it straight out. Once you've removed the paper, it is time to excavate the clay. Depending on how much clay you used, you might be able to pull back the tinfoil and remove entire sections of the sculpture at once. If not (if the clay is too thick/heavy) go back through with your sculpting tools and dig the clay out bit by bit until you can pull the rest away with the tin foil.
Next you need to prepare the papier mache. This step is twofold. First, you'll want to prepare the paper bags. You can also use newspaper, but when making masks I prefer to use brown paper bags because they are stronger, require fewer layers, and generally are faster to apply. To make the bags easier to work with, I crumple them significantly. The point here is to start to break down the fibers of the bags so that they absorb more of the papier mache mixture and to make the bags more flexible so that they are able to fold around the shape of your mask. The image to the right shows three paper bags crumpled to varying degrees. Ideally, you want your bags to look like the last one on the far right - like an old map or a worn piece of fabric. 
I try to use at least three layers of bags, sometimes a few more depending on the mask, before letting the mask dry. As the glue dries I like to refine the details even more (this is especially necessary if your mask has creases because the bags will pull away and flatten out as they dry - try and monitor the mask every few hours). The papier mache should take two to three days to dry completely though the outside should be dry overnight. However, even if the outside is completely dry, it does not mean that the inside will be too. I've had a few occasions when I've removed the mask too soon and it's shape will warp because the inside won't have anything to dry against. It is better to be safe here and wait a little longer. 
The first thing I like to do on a large costume project is to make the mask or in this case, the face. Sculpting and covering the face is the most time consuming part of the process (so I start on it early to make sure I have enough time to fully devote to it) and I'm able to begin to develop the character of the entire costume as I work. I'm going to refer back to the mask making tutorial that I wrote last year since much of that information applies here. But this time I have pictures! Today we're following the process of creating Bernard
The armature that I use (pictured above) is a 3/4" piece of pipe, screwed into a floor flange, that is attached to a Lazy Susan. I like working on the Lazy Susan because it allows me to rotate my piece while I work to really make sure that I'm sculpting in three dimensions. But anything will work as long as it provides a good sturdy base for the armature.
Next you get to start playing with clay! Treat this like any other sculpting project. Cover the general area of the mask in a layer of clay and then begin to build up the forms. Use whatever sculpting tools you have available to refine the shapes and add details. Here I used the Where The Wild Things Are book and my preliminary sketch as references. Just keep refining the form until you have the look that you want. Keep in mind that if you are creating something with lots of cracks and creases, you may want to make them more exaggerated since you will lose some definition when you add the papier mache.
Here's my finished clay base for Bernard. I started a video of this process as I was making Moishe, and as soon as that is finished I'll post it here as well. Up next: Covering the Mask!
