This resin was typically used to partially impregnate mica splittings that were laid down on a thin, pliable sheet of backing material, such as rice paper or supercalendered rope paper. Many other supporting materials, including plastic films, synthetic resin papers, woven glass cloth, glass fiber paper, etc., may be substituted on one or both sides of the sheet. Tapes cut from these sheets were wrapped onto coils to build up a few or many layers, depending on the service voltage of the coil design. The tapes were permanently flexible and, with proper storage before use, did not age, harden, or deteriorate significantly at warm or low temperatures for appreciable periods of time.