Magnetic Viewing Film 6 inch x 3 inch - Magnetic Field Display
Magnetic field viewing film...COOL!!!6 inch x 3 inch rectangular film
From Wikipedia, the free encyclopedia
Magnetic field display viewing film is used to visualize magnetic fields. It is a translucent paper-like substance which makes magnetic fields visible. Most are made from a plastic film that contains a ferromagnetic slurry of fine nickel particles that align themselves along magnetic field lines.
Some varieties appear brighter green, while others turn darker black, when in the presence of perpendicular field lines. This enables visualization of the field strength and behavior.
The general principle of operation is that magnetizable nickel particles are suspended in a colloidal form in a gelatinous material. This allows enough freedom for the particles to align with an externally applied magnetic field - thereby displacing the colored fluid and causing a color change at the surface of the film.