Indiana Mineral Wool Helps Save Energy (HI-05)
Mineral wool has been manufactured in Indiana since 1897. As many as 16 plants were operating in Indiana in the 1920's and 30's, and the state led in production of mineral wool. Limy shale from nearby quarries was crushed and melted in furnaces. Air streams blew the molten rock into long fibers resembling wool, which was sold loose or in batts (blankets) for insulation. "Rock" wool also was used in making "corkboard", felt, rock-wool cement, plaster, and brick.

Manufacturing methods are similar today, but blast and steel furnace slag has replaced shale as a raw mineral in the six remaining manufacturing plants. Slag melts at a lower temperature than shale, requiring less fuel.

Energy shortages increase our need for well-insulated buildings. Mineral wool produced from plentiful Hoosier raw materials helps meet that need.

Our Hoosier State Beneath Us: Historical