Graphite Foil: Natural Graphite Soaked in Sulfuric-Nitric Acid, Flashed at 1000 C and Rolled Without Binder (Shane, Union Carbide, US 3,404,061)

Graphite is a stack of carbon sheets held only weakly together. Acid creeps between them; flash-heated, the trapped liquid bursts the stack open into fluffy worms a hundred to three hundred times taller. Pressed, the worms lock into a flexible, pure graphite sheet with no glue at all. Result: flexible graphite foil about 10 mils (0.25 mm) thick, about 60 lb/ft3, smooth with a metallic lustre. Source: Shane, Russell and Bochman, US 3,404,061 (Union Carbide, 1968), Example III. Picture drawn by Youblob.