hello PF, Do any of you know about those green films that show you the magnetic field lines of a magnet? I understand the principle of how they work, but I was wondering about how they are made. Here is a brief description that I found on the web: A unique process of micro-encapsulation was developed which allows a very thin 2-mil layer of magnetically sensitive slurry to be bonded to a 5-mil sheet of plastic film. In the encapsulation process, colloidal nickel particles suspended in the slurry become engulfed within gelatinous membranes. The slurry is then coated onto the plastic film and allowed to dry. After complete drying, the particles maintain freedom of movement within the gelatinous membranes. My inquiries: It seems that this is a plastic material that is coated with a ferrofluid, right? And the "gelatinous membranes" are something similar to a common surfactant used in making ferrofluid? Or is it something else? Besides Nickel and plastic, there is only one component? Or two (or more)? What are they?