I received a new travel mug for Christmas, from a much-touted brand, so naturally I wanted to know whether it lived up to its reputation.
1 - Heat 2 cups of water to a set temperature (150 degrees, or as close as possible). Divide the liquid into the the tumblers, with each receiving 1 cup. This is just under half full. The reason I picked this amount was that this seems to be the tipping point where insulated mugs begin to lose the battle with lukewarmness.
2 - Using a meat thermometer, measure the temperature of the fluid at the center of mass, using as uniform sampling techniques as possible.
3 - Record the temperatures on your fridge white board.
4 - Consider transferring the data to an excel spreadsheet so you can generate handsome, informative graphs.
5 - Get back to editing a story instead.
"C" (a Contigo autoseal) wins by a small margin in both the "no lid" (left) and "lid" (right) conditions. "Y" (a Yeti rambler) puts in a decent performance but is edged out. After 30 minutes, the Contigo's liquid is 3 degrees warmer than the Yeti's.
Not pictured: When temperatures were tested after three hours, the Contigo still had a 3 degree advantage (107 degrees) over the Yeti (104 degrees).
The Yeti experiences a significant decline in temperature initially; after that, the two tumblers cool at a fairly constant rate.
I theorize that the Yeti has a larger thermal mass, causing initial cooling as heat is drawn out of the liquid to raise the temperature of the tumbler. Heating both mugs before the liquid is added might give different results, but I will leave that important work for other scientists.