To determine the actual freezing temperature, at 4.4°C, most of the oils will not harden or form any crystals. At 1.7°C, many will firm enough that they could not be poured but were as soft as butter at room temperature. As the temperature lowers, more components of the oil solidify. At -10°C, the oils gets hard enough that a fork cannot not penetrate them. Determining at what point to call the oil “frozen” is a matter of semantics because this slow increase in hardening as the temperature is lowered is in sharp contrast to a pure substance such as water that switches from a liquid to solid phase at an exact temperature.