Hard graphite insulation is a rigid, dimensionally stable insulation material composed of graphite fibers bound with a carbon-based matrix. After undergoing carbonization and graphitization, Schunk hard felt can withstand extreme temperatures of up to 2,800°C. It is commonly used to manufacture self-supporting plates, hollow cylinders, and custom geometries, particularly in high-temperature furnace construction.

In contrast, soft graphite insulation offers superior flexibility and ease of processing. Its exceptional conformability allows for intricate shaping, making it ideal for insulating complex system designs. Additionally, specialized shapes can be mass-produced using precision punching techniques. Through chemical vapor infiltration (CVI), soft felts can be reinforced with carbon, converting them into rigid, self-supporting structures.