When two-inch quadraplex video tape recording was first introduced by Ampex in 1956, it could not be physically cut and spliced simply and cleanly as film negatives could be. One error-prone method option was to cut the tape with a razor blade. Since there was no visible frame line on the 2-inch-wide (51 mm) tape, a special ferrofluid developing solution was applied to the tape, allowing the editor to view the recorded control track pulse under a microscope, and thus determine where one frame ended and the next began.