The Tinkering Studio at The Exploratorium in San Francisco has a wonderful light box tinkering activity. You choose objects that cast interesting shadows, arrange them behind a translucent screen, and shine a small bright light on them. Place some of your objects on a slowly turning motor (blend door motors scavenged from junkyards are the best!) and the results are mesmerizing.

Here is how I built an inexpensive light play box that packs flat when not in use.

Materials:

a large, sturdy cardboard box with a display window. I got my box from Costco. Its about 23" x 12" x 15"
a 21" x 30" sheet of mylar from the art supply store. I had to buy a 42" x 30" sheet and cut it in half. It was 0.004 mm thick and double matte. I think white butcher paper might work as well.
12 brass brads (they are used to fasten papers- look in the office supply section)

Step 1: Punch Holes for the Brads

Punch holes through each of the 8 corners of the box where the cardboard flaps overlap. I used an ice pick.

Step 2: Pry the Glued Flaps Apart

Pry all of the cardboard flaps apart. You will put them back together with brads. The flaps are hot-glued together. Use a sturdy tool!

Step 3: Cut Each Back Flap to Make Doors

Make a cut in each of the back flaps so that a “door” can be left open but the top corners can be re-fastened.

Step 4: Cut a Larger Display Window (optional)

Your light display will be more beautiful, but the box won't be sturdy enough to stack one on top of another.

Step 5: Re-fasten All the Cardboard Flaps With Brads

Step 6: Prepare the Mylar

Use a hole-puncher to punch holes in each corner of a 21"x 30" sheet of mylar or some other translucent material, even white butcher paper . You may need to cut the sheet smaller to fit inside your box.

Step 7: Insert the Mylar Screen

Place the mylar inside the box in a U-shape. Mark inside the box where the 4 mylar holes touch the cardboard, then punch holes into the cardboard. To attach the mylar to the box, put brads through the holes in the mylar and cardboard.

Step 8: The Finished Light Box

Find some things that cast interesting shadows and put them in the box. Shine a small bright light (I use an extra bright LED) on them and view from the front. Try adding another light, or colored lights. Put some objects on a slowly turning motor-spectacular! Try stacking two rows of boxes (as long as they are not too heavy)