Wire Enamel: Polyvinyl Formal and Cresol Resin in Solvent, Jackson and Hall 1938

GE's 1938 magnet-wire enamel: 10.67 % polyvinyl formal and 5.33 % cresol-formaldehyde resin dissolved in cresol and a hydrocarbon solvent, stirred until clear and viscous, then filtered. Wire drawn through it and baked at 250–500 °C, several passes, gets a tough, flexible insulation. We use benzene, one of the solvents the patent allows. The picture: our diagram of the mixing.