the composition of vinyl used to press records (a blend of polyvinyl chloride and polyvinyl acetate) has varied considerably over the years. virgin vinyl is preferred, but during the 1970s energy crisis, it became commonplace to use recycled vinyl. sound quality suffered, with increased ticks, pops, and other surface noises. other experiments included reducing the thickness of lps, leading to warping and increased susceptibility to damage. using a biscuit of 130 grams of vinyl had been the standard. compare these to the original columbia 12-inch lps (ml 4001) at around 220 grams each. besides the standard black vinyl, specialty records are also pressed on different colors of pvc/a or picture discs with a card picture sandwiched between two clear sides. records in different novelty shapes have also been produced.