Acetate Disc - Physical Characteristics

Physical Characteristics

Although once produced in a wide range of sizes (from less than 7 to more than 16 inches in diameter) and sometimes with glass core discs, the examples most commonly encountered today are 10 or 12 inches in diameter and consist of an aluminum core disc coated with black nitrocellulose lacquer. Blank discs were traditionally produced in several different grades, with the best and costliest grade featuring the sturdiest core, the thickest coating and the most perfectly flawless mirror-like surfaces. These top-quality blanks were intended for cutting the master discs which would be processed into metal parts for pressing ordinary records. Second-quality blanks were considered adequate for non-critical uses such as tests and demo discs. Lower-grade blanks were formerly made for home use by amateurs and may be very thin and flexible, may have a cardboard rather than a metal or glass base, and may have noticeably dull or slightly orange-peel-textured surfaces. Regardless of grade, there is almost always at least one extra "pilot hole" in the label area, meant to be engaged by a special pin which prevents the disc from slipping on the turntable during the recording process. Pilot holes are often hidden by labels applied after the recording was made, but can usually be detected by careful inspection of the label or by holding the disc up to a light bright enough to penetrate the labels.