You can make double exposures with an Image/Spectra Camera and Impossible film. It's a very easy and fun technique.
What you need
1 Image/Spectra Polaroid Camera
1 Impossible B&W or Color Film for Image/Spectra Cameras
How to do it
Step 1 Take your Polaroid Image/Spectra camera and a pack of Impossible B&W or Color Film for Image/Spectra Cameras. Set the lighten/darken adjuster on the back of your camera to darken.
Step 2 Choose your subject, press the shutter button and do not release your finger from it.
Step 3 Keep on holding the shutter button and open the film compartment door. You can now release your finger from the shutter button.
Step 4 Close the film compartment door.
Step 5 Take a second photo to compose the double exposure. Let the image eject from the camera.
Step 6 Let your image develop and enjoy your double exposure!
You can also make triple or quadruple exposures but the overall picture might be overexposed.