So was recently thinking about the beer cooler sous vide method and had a thought:
While heating the water to put in the beer cooler, if you were to place an object with a high heat capacity (e.g. a ceramic coffee cup) in the water, heat both to the desired temperature and then place them in the beer cooler, would that help keep the water at a more constant temperature?
In other words, since you are replacing some of the water with a material at a higher heat capacity at the same temperature that would in turn keep the rest of the water warmer for a longer period, correct?