How to make a smoke box
Obtain or construct a wooden box 30 cm high and wide, and 60 cm in length.
a Fit panes of window glass in the top and front of the box. The glass panes can be held in place with silicone sealant.
b Leave the back open and cover with loosely hung black cloth that drapes like a curtain. Hang this curtain in two sections, with a 10 cm overlap at the centre of the box. Paint the inside of the box with mat black paint.
c Cut a window 10 cm high and 5 cm wide midway between the top and bottom of one end, and 8 cm or 10 cm from the glass front. This window lets in light rays.
d You can cover the window with different kinds of openings cut from cardboard and fastened with drawing pins.
(Instructions from the New UNESCO source book for science teaching)