A client seeks an insulating coating for a ceramic substrate and a method of applying it. Electrical leakage from one side of the substrate to the other causes damage. A thin coating is preferred for the application, but the critical specification is the relative permittivity of the coating, which should be smaller than 20 micrometers. A proposed solution must cover 100% of an area approximately 0.5 × 0.5 m, with an average surface roughness (Ra) ~500nm, and peak-to-valley measurements of ~5 micrometers. Operating conditions for the coating after application are at near-room-temperature.