Just ran a test using a Lee 6x9mm mold, K Type thermocouple in the 3rd hole and a TM6801 Thermometer. Used a tiny bulb type thermocouple so it would fit through the sprue hole. Links below.
Heated mold to 250f in the sprue, which I know is way cool but I'm a bit short of time right now. Shelf temp was 85f.
At 2, 5 and 10 seconds I could not see a drop. At 30 seconds on the shelf it was down to about 240f. At a minute it was down to about 220.
http://www.ebay.com/itm/Digital-Ther...item4ae2c0aa5a
http://www.ebay.com/itm/K-Type-Therm...item54081c4219