What indicates that fries are done cooking, besides using timers?

Fries floating to the top of the basket is a reliable indicator that they are done cooking. This phenomenon occurs because the cooking process causes the water absorbed by the potato to turn into steam, which then pushes the fries upwards as they become less dense. When they rise, it signals that the internal moisture has been sufficiently cooked off, contributing to their desired texture.

While the aroma of fries can be an indicator of doneness, it is subjective and can vary based on personal perception. Uniformly cut fries are important for even cooking, but they do not necessarily indicate when they are done. Although golden brown coloration is a standard expectation for fried foods, there can be variables that affect appearance, and this alone isn't the most reliable sign of doneness without considering other factors like texture and internal temperature. Thus, the floating of fries in the oil serves as a clearer and more consistent cue for confidently determining when they are properly cooked.