Vintage acid tabs from the 1970s. These pieces of blotter paper are impregnated with lysergic acid diethylamide (LSD) or 'acid'. LSD is a psychedelic drug and a hallucinogen. First synthesised in 1943, it is non-addictive and non-toxic, but its effects are unpredictable. LSD was originally sold on anything from sugar cubes to biscuits. After its ban in the 1960s, drug dealers were sentenced based on the weight of the substances containing LSD. A lightweight method for distribution first appeared in San Francisco, USA. Pieces of blotter paper were divided into squares, each containing a 'trip'. The blotters could also be printed with a dealer's chosen image (shown here).