This is kind of a specific question relating to an experiment I'd like to setup. I have an old thermos, and I thought it would be interesting to see how efficient it is at insulating its contents. I did an ad hoc experiment using boiling water and a candy thermometer, but I only sampled the water twice with any accuracy. What I would like to know is there such a thing as a small water proof/resistant, heat resistant, time-interval recording thermometer? Just some small device that would record the temperature for 24 hours or so at some interval. I have no idea where to look for something like that. Any design ideas would be appreciated as well.