Coal tar
Historical Development: The asphalt-prepared roofing industry had its beginning in Sweden more than a century ago, when roof boards were covered with paper treated with wood tar. Later, in Germany, paper was coated with varnish, surfaced with finely ground mineral matter, and used as a roofing material. In the United States, asphalt was used to waterproof duck fabric in the early part of the nineteenth century. The first recorded use of melted asphalt for impregnating duck fabric in this country was in 1844. About this time roofs composed of sheets of sheathing paper treated with pine tar and pine pitch, and surfaced with fine sand, were being laid. Coal tar and coal- tar pitch were later substituted for the pine tar. These were the forerunners of the present asphalt and coal-tar-pitch built-up roofs. It is not known definitely when felt was first substituted for sheathing paper or when asphalt was first used as the impregnating agent, but it is known that the first asphalt-prepared roofing, that is, roofing manufactured ready to apply, was marketed in 1893. The first roofing was not surfaced.