Cylinder recordings were the first commercially viable sound recordings available. Beginning with Thomas A. Edison's tinfoil cylinder in 1877, cylinder development varied widely in materials, construction, playback speeds, and playback devices. Early cylinders were colloquially known as 'wax' cylinders (although actually made of metal soaps). The stylus transcribed the sound wave into the wax by changing the depth of the groove that was incised. Referred to as the vertical-cut or hill-and-dale groove method, this technique was used for all cylinder recordings. The recording time available on a cylinder is determined by a combination of the cylinder's length, diameter, speed of rotation, and the density of the recording, which is measured in threads per inch (tpi). Recordings were made directly on the early brown wax cylinders. Methods for mass production were limited and often resulted in poor quality records.