It's almost like a magic trick. A sheet of fabric is hung and stretched. The outer face of this "wall" is well lit.
The area behind the wall is kept completely dark.
When the area behind the scrim is lit, anything present is visible THROUGH the scrim. It's that simple.
Trigger one light, and something can "appear."
By definition, scrim is a light - weight, open woven fabric - sheer.
Examples include a bridal veil, or fine gauze. This fabric can be painted to blend into the scene,
or painted to stand out (such as a false door.)
I first read about the use of this while visiting www.doombuggies.com.
In here, you'll find secrets of Walt Disney World's Haunted Mansion revealed.
The final scene in the "stretching room" uses this technique.
These images represent the effect before and after triggering the light behind the scrim wall.
We built a simple box using 1/4" hardboard and 2X2 lumber.
The front wall of the box was a scrim wall ... nothing more than a sheet of scrim stretched
and stapled to a 2X2 frame. (We used black scrim because the haunt walls were black fabric.)
We used a 12 volt DC relay as a switching device (with a switch mat as the actual switch.)
The front lights are connected to the Normally Closed circuit using a power strip.
The Back lights and effects are connected to the Normally Open circuit (another power strip.)
A mat switch was placed directly in front of the Scrim Box.
When stepped on, the wall seemed to disappear, and the "Monster"
on the other side was VERY visible, and a screaming sound effect was played.
We added photos to the 2002 Prop page which may help explain this
simple relay/switch a little better. Go To Switches
The magic part of this theater trick is simple - The light enters the threads of the fabric at a steep angle,
and the rays "Bury" themselves in the open weave. The audience sees the outside light reflecting off the fabric.
They call it (no-see-um) netting so this blended into the Haunt walls perfectly.
In a four - foot wide hallway, a monster appearing from within the wall right next to you might be a bit unnerving.
My partner - in - crime, Brian, thought it would be fun to get in the box with the monster, and bring the mat switch inside with him.
This way, HE could control the lights. Now the static monster was animated. We laughed so hard between
groups of guests, it's amazing that we didn't ruin the surprise. From inside the box, people walking by are clearly visible,
but they have no idea what's about to happen.
Proof that this effect works :
A man working at the haunt walked down the hallway while I was inside the box.
He knew where the switch was, and noticed it didn't trigger the effect. He stomped around for a while,
(almost dancing) looking for the switch. Eventually I decided the poor guy could use a good laugh.
I triggered the lights and let out a scream... This big man could really jump...
he failed to see the humor in it...
Update October 29, 2002
We used the scrim effect again in the Hinton Haunted House 2002.
This time, we didn't use a box at all. We simply stretched the scrim across a corner in the hallway.
The board hanging from the ceiling is positioned to block the light, making sure it doesn't penetrate the scrim wall.
This project was much simpler than the "box" project of 2001, but the effect was just as good.
Above is a photograph of the effect without using a flash.
Brian wore dark clothes, and a black wide-brimmed hat.
He covered himself with a second, smaller sheet of black scrim.
When visitors rounded the corner, he turned the flashlight on and
illuminated his face from below... all the while blurting out his nearly famous primate-esque
"oooo-ahhhh-aahhhh!!!!"
This photo accurately shows what the guests saw - just a face appearing
from within the "wall."
2003 Scrim Effect Usage:
For the 2003 Haunt, we stepped it up slightly by masking the scrim wall
with camouflage netting. It helped blend the wall with the theme of the room,
and added to the surprise. The room effects were triggered from behind the scrim wall,
along with Brian's famous incantation(s).
2004 Scrim Effect
By far ... my personal favorite example of our attempts to date.
Although these photos were taken slightly before darkness fell,
you should know that the effect only improved in the dark!
We hung the scrim in the window frame and positioned a Bucky skeleton
inside the house. A white pinspot light was placed directly under the prop,
which was manually switched "on."
It was such a nice effect, we decided to improve on it by adding
a second (red) pinspot light illuminating a cheesecloth backdrop, and a
high velocity fan to add some motion to the scene.
... still within the confines of economical-and-easy, but yielding better
results than expected!