Envelope deformer problem for mouths

I’m trying to figure out a good system for using envelope deformers for lip synch. I can make a horizontal ellipse and fill it and then use an envelope deformer to change it’s shape. If I collapse it vertically past a point, the internal paint shows up outside the outline. This makes it impossible to use the deformer to get a closed mouth. Is there a trick I’m missing with the deformer? If not, is there a way of switching between a deformed mouth and an undeformed mouth in order to get a closed mouth?

A few months ago, I asked that to support on how to deform a kite, to make it spin, and “bumped” on a problem similar to yours, and that was their answer:

Hi Mauricio, The envelope deformer is not designed for extreme changes. The reason you are seeing this strange artifact is when you push the edges together it pushes the image beyond the opposite side of the deformation edge. A really simple way to make the kite narrower is to just add a peg above and reduce the X-scale value. In the case where the deformation needs to be more organic, use the Mesh Warp instead. regards, -ron

Apart from that in order to answer to your question

“If not, is there a way of switching between a deformed mouth and an undeformed mouth in order to get a closed mouth?”

Yes there is. You actually just have to create a new drawing for your closed mouth which, by default, won’t be affected by the deformation chain of the previous drawing.