A 19th Century clear crystal drinking glass by John Northwood, the slender round funnel bowl acid etched with a Greek Warrior with shield and spear between repeat borders, mounted to a slender slice cut stem abov e a circular spread foot. Etching glass by drawing a pattern in a layer of wax on the surface of the glass and then plunging it into hydrofluoric acid was first practised in the late 18th century. The process was developed commercially in the 1840s. By 1861 John Northwood (1836-1909) and James Northwood (1839-1915) at Wordsley, West Midlands, were among the first major producers to use it extensively. They had earlier invented the template etching machine for inscribing the pattern through the wax. With the invention in 1864 of a gear-driven, geometric etching machine, interlocking patterns such as loops or the ever-popular 'Greek key' border patterns were applied to virtually all table glass. They were used especially on the new paper-thin glass that appeared in the 1870s.