If you are the experimental sort, you might want to try some experiments to see how different forms of insulation compare to a thermos. Or you might want to try to improve the performance of a thermos. "Can you keep hot coffee hot all day?" is the ultimate question: If you can answer this question affirmatively it is likely you could base an entire business empire around it...
One avenue of investigation involves understanding your thermos better:
- Start with a thermos.
- Fill it with boiling water and cap it.
- Measure its temperature with a thermometer every hour or two and see what the temperature graph looks like.
If you put the thermos inside a small foam cooler, does that change anything? What if you store the thermos upside down during the day -- what effect, if any, does that have?
Another thing you can try is a set of experiments to find the insulation values of different materials. Find several jars that hold the same amount of liquid as your thermos and try insulating them in different materials. Try things you have around the house like foam, wool, aluminum foil, plastic, newspaper, etc. Also try combinations of these materials, and different thicknesses. You will learn a lot about the heat conductivity of different materials!