The first experiments were conducted by Russian scientists in the sixties who confirmed that some light yellow diamonds turned colorless when heated to temperatures of up to 1200°C under pressures reaching 5500 bar. This first research also showed that light green and yellow-green diamonds turned a deeper shade of green.
During the 1970’s General Electric researchers worked on the treatment, resulting in two United States patents by the end of the decade. In 1983 De Beers followed with a patent resulting from their own research. The overall focus was on decolorizing off-color diamonds.
The methods and exact treatment process remained a mystery and the trade was left in confusion until 2000 when various reports on HPHT diamond enhancement were published in gemological magazines. Research and experiments continue to this day and since 2000 it has become clear that HPHT in combination with irradiation can produce a vast range of colors.