is it okay to put Foam for the talking mouth?  I've been watching Paul Louis Muller way of making the mouth board.  But can you do FOAM for the mouth too?       

Forgot to say, I am making a hand puppet/glove puppet.  That's why I am asking.  You'll see soon. 

Yes, you can. I do it - cardboard buckles after a lot of use. I found using thin foam (craft foam, or Foamies) gives a good flexibility to the mouth but it's still sturdy.

You can actually see how I do it here:
http://www.schoolofpuppetry.com.au/tutorials.php/how-to-make-a-muppet-type-puppet-human-foam-puppet-pattern
You can download the instructions/free pattern for making the mouth using foam.

I should mention too that there are many other materials you can use, but one of the favourites mentioned by members here is gasket rubber.

That's what I have-thin foam.  Thank you, Na.  Where can I find rubber.  Looking for red rubber at Hobby Lobby.  None there.   

Not sure about the rubber - a good search of the forums might come up with suggestions. Not being in USA myself it's always hard for me to make those recommendations myself.

You can use thin plastic too I found here a plastic that I can use. I want to be able to wash the puppet by hand....
Here is a link look only to the picture the rest is in Dutch and not important for this
http://www.nefab.nl/Inzetstukken.aspx

That's what I have-thin foam.  Thank you, Na.  Where can I find rubber.  Looking for red rubber at Hobby Lobby.  None there.   

Try a hardware store........ they sell whats called gasket rubber in sheets or in kits. What are you using it for?

http://www.amazon.com/0-RED-RUBBER-GASKET-KIT/dp/B002FYCBOC

I bought the rubber that she's describing at Menards. I don't know if you have any of that chain anywhere near you as they're pretty much in the heart of the Midwest, but if not then I would think that you could find it at a Lowes or Home Depot.

http://www.menards.com/main/plumbing/rough-plumbing/installation-maintenance/faucet-repair/washers/rubber-gasket/p-1339788-c-8544.htm

I found the rubber at a small hardware store, it is an Ace affiliate.  They sold it by the foot.  Home Depot and Lowe's in this area carry it in one size only (a small piece).

What Gompie is showing is called corrugated plastic (used a lot for signs, Wal Mart has the signs). 

I tried to find gasket rubber here in Holland but the look to me if I come from an another planet (I do but they don't know that). I don't know if gasket rubber is flexibel, you can cut it........
I don't if it is the same but I use for baking a silicon (rubber) plate. It is very flexible and you can buy it in different colors. A few mm thick and you can cut it with siccors.

I think you'll find it difficult to get anything to adhere to the silicone...

Gompie

The baking mats I have (probably just like yours) are similar in thickness to the gasket rubber and about the same flexibility.  I think it would work.

You might look in a plumbing supply for the gasket rubber. 

I wonder: has anyone here tried polypropylene? It's what I'm working with at the moment for shadow puppets and I'm finding the sheets extremely flexible (ie. bendable without breaking) and sturdy.

I'm not sure I would use it for muppet-type puppet mouths, but then I've not actually thought about it til now.

I use plastic lids from ice cream and food containers. The plastic is thin, easy to cut and flexible. AND best of all FREE!!

LJ,
Do you cut the lid in half and add a hinge or do you just fold it over? Just curious.