From Rare-earth Information Center Newsletter
Iowa State University
December 1, 1998
Magnetic Field Viewing Film
The ability to visually see DC magnetic field patterns provides advantages to manufacturers in the area of quality control, researchers in magnetic field analysis, and educators in illustrating the behavior exhibited by magnetic fields. Magne-Rite, Inc. provides a flexible film that allows the user to visually determine the static magnetic fields of hard and soft permanent magnets, as well as accompanying magnetic fields associated with current-carrying wires. The company's viewing film is possible through a process that employs the micro-encapsulation of colloidal nickel which gives the paper-thin plastic film its flexible nature. The film allows the viewing of magnetic fields without the need for bulky, rigid magnetic field viewing devices.
In order to produce the films, a slurry of colloidal Ni particles that are engulfed within gelatinous membranes is prepared. A 2 mil coating of the slurry is then applied to the 5 mil thick plastic film and allowed to dry. After drying, the nickel particles maintain their freedom of movement within the gelatinous membranes. When a dc magnetic field is applied to the bonded film, the Ni particles congregate in alignment with the magnetic flux lines that emanate from the magnetic source, which show up as a dark image on the film. Once the film is removed, the particles are free to move around in their cells, which erases the image. The film is sensitive enough to show magnetic fields as low as a few gauss. The company claims that this film is particularly useful in identifying changes in magnetic polarity.
The 0.006 inch-thick film is green in color and is available in 12 or 18 inch rolls, and 12 inch by 12 inch sheets. The greatest advantage of these films lies in their ability to conform to magnetic surfaces with high degrees of convexity and concavity and cut to a desired size.
