Why are thermos’s better at keeping things cold rather then keeping things hot ?
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Insulation (the blocking between the hot and the cool sides in a thing) works by slowing down the speed of the heat getting to the cold side. It will get there, the heat just goes slower the better the insulation AND it also goes slower if the difference between the sides is smaller! It is like a ramp and a fuzzy ball. If the ramp is not steep the ball’s fuzz can slow it. The steeper the ramp, the less the fuzz helps slow the ball.
Now. A hot drink at 145 inside the thermos is in a 70 degree room so the “ramp” is 75 degrees of heat difference. But a cold thing is probably 36 F compared to the 70 degree room. A difference “ramp” of just 34 degrees. An easier job for the insulation to accomplish is to keep heat from rolling down that smaller ramp.
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