PINHOLE INVESTIGATIONS

Making a Square Tabletop Light Source

©1998 Exploratorium

These instructions allow you to make six Square Light Sources.

Materials
(for six Light Sources)

  • 6 cardboard boxes of graduated size*:

    8-1/2" x 8-1/2" x 8-1/2"

    9" x 9" x 9"

    10" x 10" x 10"

    10-1/2" x 10-1/2" x 10-1/2"

    11" x 11" x 11"

    12" x 12" x 12"

  • 6 clear light bulbs, each with a different filament. Suggested bulbs include:

Name

Watts

Catalog No.

Filament Shape

G.E. Crystal Clear

150

150A/CL

vertical

G.E Ceiling Fan Light

60

60A15/CF CDC 2

C-shaped

ABCO Chandelier Bulb

60

60Bll/CD

V-shaped

Ace Tubular Bulb

60

60T10

pentagonal

Abco Clear

75

75A19 Clear

horizontal

Ace Decorator Clr.Globe

60

60G25 Clear

C-shaped

  • utility knife or exacto knife
  • metal straight edge
  • clear strapping tape, 2" wide-this becomes a structural element; it makes the top hole stronger and protects the box surface around the windows from the repeated use of tape
  • 6 clamp light cords: Eagle brand #484 suggested, but any clamp light will do if you remove the clamp and the reflector
  • cutting surface to protect table (scrap of masonite or wood)
  • (optional) duct tape for reinforcing the bottom edges
  • (optional) band saw for cutting flaps off

 

Making the Square Light Source

  1. While the box is still flat, cut flaps off one end with a band-saw, utility knife or exacto knife. If using a knife, use the metal straight edge to guide the cuts. Straight cuts will prevent light leaks. The cut edges will become the bottom of the light box (Figure 1A).

  2. Make a template to use when cutting the windows, a rectangle measuring 3-7/8" x 2" (Figure 2).

  3. Next, while the box is still flat, you need to draw and then cut out the windows. The location of the windows is critical. Keep the following pointers in mind:
    • All windows are the same size, 3-7/8" wide and 2" high.
    • All windows are centered with respect to the sides of the box, but the windows in each box are of at a different height so as to insure that the images from the light bulb will appear on the table or screen.

    Now, using the template, draw the windows on the box, using the following guidelines for each box (Figure 1B):

    Size of Box

    Distance between bottom of window and bottom of box (inches)

    8-1/2" cube

    1-1/2

    9" cube

    1-3/4

    10" cube

    2

    10-1/2" cube

    2-3/4

    11" cube

    3-1/4

    12" cube

    3-1/4

  4. Cut out the windows.

  5. Make a frame around each window with 2" strapping tape. This will protect the box from tearing with repeated use of tape to attach the paper or foil masks (Figure 1C).

  6. With the box still flat, cut four 1" square holes in the top for ventilation of the box (Figure 1E).

  7. With the box still flat, measure the center of the two flaps. Make an arrow-shaped cut, with the point of the arrow at the center mark (Figure 1D).

  8. Fold to construct the box, and stand it on the table, with open side down (Figure 3).

  9. Tape seam where flaps meet, outside and inside of box, then add a short piece of tape across the arrow-shaped cut. This will become the hole for the light fixture (Figure 3A).

  10. Make 4 cuts where the strapping tapes cross, forming an asterisk shape, to conform with the cuts in the box (Figure 3B).

 

When the box has been used several times, reinforce the area around the hole with short pieces of strapping tape, and re-make the cuts to reinforce the hole for the light fixture.


* Note: Making these in graduated sizes facilitates storage since boxes fit into each other, however they can be all of one size. The light sources made from boxes are lighter, more inexpensive, and easier to store, but the round light sources made from molds used for cement are more durable.