Even though scientists didn't know the exact source of electricity. they learned that they needed materials that could conduct this mysterious force and block its flow or keep it from leaking. Metals were identified as good conductors, and they also could be formed into long wires because of their special properties of ductility and malleability. As discussed in Chapter 2, ceramics and glass were identified during the earliest experiments as excellent insulators for electricity and were used throughout the 1800s to support electrical invention and innovation.