The effect is named after Tanzanian scientist Erasto Mpemba. He described it in 1963 in Form 3 of Magamba Secondary School, Tanganyika; when freezing a hot ice cream mix in a cookery class, he noticed that it froze before a cold mix. He later became a student at Mkwawa Secondary (formerly High) School in Iringa. The headmaster invited Dr. Denis Osborne from the University College in Dar es Salaam to give a lecture on physics. After the lecture, Mpemba asked him, "If you take two similar containers with equal volumes of water, one at  and the other at , and put them into a freezer, the one that started at  freezes first. Why?" Mpemba was at first ridiculed by both his classmates and his teacher. After initial consternation, however, Osborne experimented on the issue back at his workplace and confirmed Mpemba's finding. They published the results together in 1969, while Mpemba was studying at the College of African Wildlife Management.
Mpemba and Osborne described placing  samples of water in  beakers in the icebox of a domestic refrigerator on a sheet of polystyrene foam. They showed the time for freezing to start was longest with an initial temperature of  and that it was much less at around . They ruled out loss of liquid volume by evaporation and the effect of dissolved air as significant factors. In their setup, most heat loss was found to be from the liquid surface.