[Hnrobert42]

I would think that the starting temperature and ambient temperature are controlling. Boiling water is three times ambient temperature. 150°F is twice ambient temperature.

The exponential decay is obvious because he started the readings at boiling. If he had started at 150°F, it might not have been as obvious that the readings were on an exponential curve.

Is that right? I didn't get much sleep and don't drink coffee. Lol