Flaking Paint

The action:
INT. THE HALLWAY - MORNING

...And we follow him into the hallway but wait as he continues on into his bedroom. Through the open doorway we hear CLOTHING RUSTLING, and when he comes back into view he is wearing his sport coat. He stops for a moment in front of the full-length mirror next to the door to scrutinize his appearance, then comes out of the bedroom towards us. Halfway down the hallway he suddenly stops, a look of consternation on his face.

NOLAN'S POV OF THE WALL AT THE END OF THE HALLWAY.

A flake of paint has separated itself from the wall at about eye level. It is small, only about the size of a dime, but we can tell from the look on Nolan's face that its size is irrelevant.

ECU OF NOLAN'S FINGER GINGERLY TOUCHING THE FLAKE OF PAINT.

With a sudden, audible SNAP it drops away in a hand sized sheet, revealing the awful puce color of the wall underneath. CUT TO the humming clock in Nolan's bedroom.

That's the sequence. I figure there will be three shots of the flake of paint: (1) Nolan's POV from about five feet away of the end wall and the flake of paint. (2) An extreme close-up of the paint chip, with Nolan's finger entering the frame to touch it. (3) An over-the-shoulder as Nolan touches the paint flake and it drops away.

I think it would be possible to cheat the wall - i.e. make a piece of false wall, if that would help.

Can anyone help me with this effect?

I mixed some plaster with 91% Isoprophyl alcohol then spread an even coat onto a piece of sheet rock that had been coated with a very thin coat of vaseline. I smoothed the plaster out and feathered the edges into the sheet rock. When the plaster had set up it was very very weak since it does not react with the alcohol. It has a slight bond because there is some water in the alcohol (about 9%). You would have to let it set up then paint it very carefully or maybe airbrush some paint onto it. To get it to crumble on cue, you could embed a few pieces of sewing thread (same color as the wall paint) in the plaster and pull them downward at the right moment. If that doesn't work then attach small pieces of paper or tape to the ends of the thread and embed them in the plaster. That way, when you pull the thread you will be causing stress on more surface area of the plaster. It will probably take a little bit of experimenting but I'm sure it will work well for you..

I just thought of something. Even though the plaster will be quite brittle, the paint that you apply over the top of it will serve to bind and seal the plaster. This will probably cause the plaster "patch" to come off as one piece instead of crumbling. The only way I can see around this problem would be to mix up some tempra paint (kind of like water colors). It doesn't have a binder so it will not keep the plaster from crumbling. If you have no choice but to paint the patch with house paint then maybe you could leave hairline spaces of unpainted plaster between painted areas. Paint the patch kind of like a jigsaw puzzle. That way, you could actually design the size and shape of the pieces that will fall off of the wall.