Not Just Asphalt?
Unlike the name “Asphalt Shingle” would imply, asphalt shingles are not made entirely of asphalt. Two types of base materials are used to make asphalt shingles: A formerly-living organic base and fiberglass base. Both types are made in a similar manner with asphalt or modified-asphalt applied to one or both sides of the asphalt-saturated base (Wikipedia). These are then covered with slate, schist, quartz, vitrified brick, stone, or ceramic granules and the back side treated with sand, talc or mica to prevent the shingles from sticking to each other before use. Some shingles have copper or other materials added to the surface to help prevent algae growth (RoofingRoger).
Organic shingles are composed of waste paper saturated in asphalt, which makes it waterproof (pacificwestroofing). A top coating of adhesive asphalt is applied and ceramic granules are then embedded into each shingle. Organic shingles contain around 40% more asphalt per square (100 sq ft.) than fiberglass shingles (Wikipedia).
Fiberglass shingles have a base layer of glass fiber reinforcing mat. Fiberglass shingles resist fire far better than the older organic shingles. Fiberglass reinforcement was devised as the replacement for asbestos paper reinforcement of roofing shingles and typically ranges from 1.8 to 2.3 pounds/square foot. Fiberglass shingles are slowly replacing organic felt shingles and in 1982 the production of fiberglass shingles overtook organic shingles (Wikipedia).
History of Asphalt Shingles
Asphalt shingles are an American invention first used in 1901, in general use in parts of America by 1911 and by 1939 11 million squares of shingles were being produced (nrca). In 1960 fiberglass mat bases were introduced with limited success, the lighter more flexible shingles proved to be more susceptible to wind damage particularly at freezing temperatures. Asphalt Roofing Manufacturers Association (ARMA) formed the High Wind Task Force in 1990 to continue research to improve shingle wind resistance (ufl).