The thing to keep in mind as you try to do this kind of thing is... to make a
scrim not show what's behind it, you probably will do better to light it from a high angle..
More light will reflect back at you if you "skim" the surface... you will catch more fibers, and it will appear opaque. Also this avoids any "bleed through" from lighting your actors.
To use it as a lighted acting space.. no forelight on the
scrim of course, and fore light the actors and space from behind the
scrim.... or sometimes depending on the fabric, direct forelight from in front of the
scrim
will mostly
go through to your actors, and they will be the predominant thing that is lit.
To get your "shadow
effect" you would to the high angle
scrim lighting to make it look opaque, and then light your actors directly from behind with no fore lighting on them.
Best example ever.. which was done without even a
scrim, just fore light, back light, and 2 towers of lights to alter the audiences pupillary diameter was when David Copperfield
Made the Statue of Liberty disappear. I'm sure it's on youtube somewhere.
You might
play with some black guaze fabric from fabric.com or some such if you don't want to do a big outlay.. I used it for my Bedford falls bridge, which had George in front of snow falling,
yet you could see the set behind the
scrim as well.