text: 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 being field tested, or used commercially. 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, the Bessel process became uneconomical after the discovery of high-grade graphite in Sri Lanka and was largely forgotten.
  Inventor Hezekiah Bradford of Philadelphia invented a "method of saving floating material in ore-separation” and received US patent No. 345951 on July 20, 1886. He would later go on to patent the Bradford Breaker, currently in use by the coal industry, in 1893. His "Bradford washer," patented 1870, was used to concentrate iron, copper and lead-zinc ores by specific gravity, but lost some of the metal as float off the concentration process. The 1886 patent was to capture this "float" using surface tension, the first of the skin-flotation process patents that were eclipsed by oil froth flotation.
  On August 24, 1886, Carrie Everson received a patent for her process calling for oil[s] but also an acid or a salt, a significant step in the evolution of the process history. By 1890, tests of the Everson process had been made at Georgetown and Silver Cliff, Colorado, and Baker, Oregon. She abandoned the work upon the death of her husband, and before perfecting a commercially successful process. Later, during the height of legal disputes over the validity of various patents during the 1910s, Everson's was often pointed to as the initial flotation patent - which would have meant that the process was not patentable again by later contestants. Much confusion has been clarified recently by historian Dawn Bunyak.