Gives the methods of test for electrical insulating materials suitable for application as coatings for loaded printed wire boards (conformal coatings). The tests are: visual assessment, properties after thermal cycling, resistance to organic liquids, coating removal, dissipation factor and permittivity, insulation resistance after damp heat, mould growth, shelf life, flammability, tackiness, loss of volatile matter, thermal ageing, insulation resistance after salt mist, extreme altitude and temperature test, electric strength.