expressions - 5 to 20 min

Hey Noddydog,
I think your overall proportions on the longer sketches look good. I also think your shading is on point, especially the 20 minute sketch.
For the teeth I recommend avoiding drawing lines between each tooth. Instead differentiate the teeth by shading on one side and highlighting the other side. There are a lot of good youtube vids for that. I think that might help your open mouth studies. Keep it up!

I like the expression in your 20 minute sketch. It captures the emotion of the reference used :)

If you feel trouble drawing people with open an open mouth. I would look into doing art studies of the skeleton head with the focus of how the jaw opens and closes. Keep up the good work!

Try more closely observing the shape of the mouth in reference. A good rule of thumb is that when open wide, as if shouting, the mouth is more shaped like a pringle in 3d space than an ellipse or circle.

Also, make sure that the jaw is properly placed, the jaw hinges right below the ear so the chin should be always the same distance from the ear lobe whether the mouth is open or closed.

I honestly think you did pretty well on the drawing on the bottom left, i could only critique the length of the jaw as if he had closed his mouth, he would probably have a mighty underbite.

In the drawing on the top right, it looks as if his jaw has travelled directly down rather than rotating at its hinge.