Dating old columbia records
The materials of which discs were made and with which they were coated were also various; shellac eventually became the commonest material.
; Recording Industry Association of America (RIAA) website _________________________________________ Any flat disc record, made between about 1898 and the late 1950s and playing at a speed around 78 revolutions per minute is called a "78" by collectors.
Collectors can identify these discs by either by listening or by means of small marks in the record surface close to the label. By around 1920 lateral cut recording was the norm; a less exacting technique than vertical cut, it produced a level of fidelity adequate to the standard of the equipment the general public could afford to buy.
The physical format of electrical recordings remained the same as that of the many acoustical ones utilizing the lateral cut technique.
In response to the vibrations of air in the horn, the stylus cuts a spiral groove in the thick wax coating of a cylinder or disc, rotated steadily by means of a crank.
The cutting process creates variations in the groove analogous to the varying frequency and amplitude of the vibrations; the stylus moves up and down in "hill-and-dale" or "vertical cut" recording and from side to side in "lateral cut" recording.