What material is used in order to release the vinyl records from their molds?
The earliest disc records (1889–1894) were made of various materials including hard rubber. Around 1895, a shellac-based compound was introduced and became standard. Exact formulas for this compound varied by manufacturer and over the course of time, but it was typically composed of about one-third shellac and about two-thirds mineral filler, which meant finely pulverized rock, usually slate and limestone, with an admixture of cotton fibers to add tensile strength, carbon black for color (without this, it tended to be a "dirty" gray or brown color that most record companies considered unattractive), and a very small amount of a lubricant to facilitate mold release during manufacture. Some makers, notably Columbia Records, used a laminated construction with a core disc of coarser material or fiber. The production of shellac records continued until the end of the 78 rpm format (i.e., the late 1950s in most developed countries, but well into the 1960s in some other places), but increasingly less abrasive formulations were used during its declining years and very late examples in truly like-new condition can have as low noise levels as vinyl.