Shellac disc

Date Range: c1897 – c1960

Shellac discs, commonly called 78s, are made from resin shellac (hence the name) and are heavier and more brittle than modern vinyl records. This makes shellac discs more susceptible to cracking and ‘shark bites’ – chunks of shellac discs breaking off. Other signs of degradation include mould, which usually occurs because of how and where discs have been stored. Many shellac discs were stored in cardboard sleeves, which retained moisture and contributed to mould developing.   

Shellac discs are usually coarse-grooved, typically either 10 or 12 inches in diameter, and play at 78 revolutions per minute (rpm) with a duration of three to four minutes per side. The rpm could vary and ranged from 70 to 90 rpm until 1925, when 78 rpm became the standardised speed. Pathé produced discs which played at 120 rpm and advertised them as having a higher volume. Other recording companies experimented with size, including 5, 8 and 20 inches.    

Pre-1925, the stylus cut onto the disc in response to the sound vibrations captured by a large horn. This was commonly known as the ‘acoustical’ era of shellac recording. In 1925, companies began recording by using a microphone and amp, which resulted in a wider bandwidth in the recording, ushering in the ‘electrical’ era of shellac recording.  

Companies like Columbia, His Master’s Voice (HMV) and Victor cut their discs laterally. Others, such as Edison and Pathé, experimented with the alternative ‘hill and dale’ method of recording with the stylus moving up and down. 

The successor to shellac discs – acetate or lacquer discs – similarly employed electrical recording techniques and were laterally cut. Both recording methods are still used in vinyl recordings today.