query: When was the first graphene production technique developed?
passage: History of graphene
Single-layer graphene was explored theoretically by P. R. Wallace in 1947. It was first unambiguously produced and identified in 2004, by the group of Andre Geim and Konstantin Novoselov, though they credit Hanns-Peter Boehm and his co-workers for the experimental discovery of graphene in 1962.[1][2] Boehm et al. introduced the term graphene in 1986.[3][4]
passage: Froth flotation
Englishman William Haynes patented a process in 1860 for separating sulfide and gangue minerals using oil. Later writers have pointed to Haynes's as the first "bulk oil flotation" patent, though there is no evidence of its ever being field tested, let alone used commercially. While in 1877 the brothers Bessel (Adolph and August) of Dresden, Germany, introduced their commercially successful oil and froth flotation process for extracting graphite, considered by some the root of froth flotation. However, because the Bessel process was used on graphite not gold, silver, copper, lead, zinc, etc, their work has been ignored by most historians of the technology. Seventy-seven year old inventor Hezekiah Bradford of Philadelphia imitated their work and patented a similar process in 1885. He had received his first patent in 1834, primarily invented machinery to separate slate from coal during the 1850s-1860s, and perfected the Bradford Breaker, still in use by the coal industry today, but it is uncertain if his 1885 patented "flotation" process was successfully introduced in the graphite deposits in nearby Chester County, Pennsylvania.