What materials are insulators made from?

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Insulators are materials that resist the flow of electric current; they must be dielectric options that stay non-conductive under operating voltages and environmental conditions. Glass, porcelain, and polymers fit this role well because they have high dielectric strength and excellent insulating properties, yet can be formed into the kinds of durable, weather-resistant shapes used on equipment and lines. Modern insulators often use polymers for their light weight and reliability, with glass and porcelain continuing to be common in traditional applications.

Metallic materials like steel, aluminum, and copper are conductors, so they don’t insulate and wouldn’t perform the protective role required. While some materials such as wood or concrete can act as insulators in very basic terms, they’re not reliable for high-voltage line insulation due to moisture absorption and deterioration over time. Ceramic is an insulating material, but as a group with moisture-sensitive woods and concretes, it isn’t the best description for the standard insulator materials used in practice.