Rock woolIn 1897, a rock wool factory in the U.S., the Crystal Chemical Works, was opened in Alexandria, Ind. Mineral wool had previously been made from blast furnace slag, but the new factory used local limestone rock in a process discovered by Charles Corydon Hall to create a sulphur-free product. The limestone was melted in a specially designed water-jacketed cupola, blown by steam pressure then allowed to cool to form fine threads. Its light, fibrous form resembled freshly-sheared sheep's wool. Being both insectproof and fireproof, rock wool was useful as a filtering material and as an insulating material for such uses as packing walls or for covering steam boilers. In 1929, the works became part of Johns Manville Corp.« |
