Why can we see through many electrically insulating materials?

Clay (ceramic)(porcelain) - This is the standard material for high voltage and RF insulators. Plastics - PVC, Cresyl ... PFA (Perfluoroalkoxy) - This substance is resistant to chemical attack, transparent and better than PTFE when it comes to flexibility. read more

An electrical insulator is a material whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily. read more

In conductive materials, the outer electrons in each atom can easily come or go, and are called free electrons. In insulating materials, the outer electrons are not so free to move. All metals are electrically conductive. Dynamic electricity, or electric current, is the uniform motion of electrons through a conductor. read more

Right side: Modern Romex cabling with polymer insulation, left side has old rubber with cloth braid sheath. Rubber used to insulate wire: Many types of rubber were used for electrical wiring and apparatus. Gutta Percha - a natural latex product was used for some time but was replaced by vulcanized rubbers. read more