pipe bowl. In addition to aficionados, reproductions of historical clay styles are used by some historical re-enactors. Clay pipes were once very popular in Ireland, where they were called dudeens. Broken fragments of clay pipe can be useful as dating evidence for archaeologists. English specialists can date a pipe to around a 20-year period. In the 1950s, the American archaeologist J. C. Harrington noted that the bore of pipe stems decreased over time, so a late sixteenth or early seventeenth centuries pipe would have a stem bore diameter of around , but a late eighteenth century pipe would have a bore diameter of around . The size of bowls also increased over time as tobacco became a cheaper commodity, and later pipes tend to be more decorated. Corncob The uniquely American pipes made from corncobs are cheap and effective, although regarded by some as inelegant. After being dried for two years, the cobs are hollowed out to form a bowl shape, then either dipped in a plaster-based mixture or varnished or lacquered on the outside. Shanks made from birch wood are then inserted into the bowls. The world's oldest and largest manufacturer of corncob pipes is Missouri Meerschaum, located in Washington, Missouri, where the company has produced the pipes since 1869. General Douglas MacArthur and Mark Twain were perhaps the most famous historical smokers of corncob pipes, as well as fictional cartoon characters Popeye and Frosty the Snowman. Corncob pipes remain popular because they are inexpensive and require no "break-in" period like briar pipes. Owing to these factors, corncob pipes are often recommended as a "beginner's pipe". Additionally, pipesmokers who wish to sample different tobaccos and blends might keep a stock of corncobs on hand to permit them to try new flavors without "carryover" from an already-used pipe, or to prevent a potentially bad-tasting tobacco from adding its flavor to a more expensive or favored pipe. Meerschaum Meerschaum (hydrated magnesium silicate), a mineral found in small shallow deposits mainly around the city of Eskişehir in central Turkey, is prized for the properties which allow it to be carved into finely detailed decorative and figural shapes. It has been used since the 17th century and, with clay pipes, represented the most common medium for pipes before the introduction of briar as the material of choice in the 19th century. The word "meerschaum" means "sea foam" in German, alluding to its natural