For maximum performance and heat retention, preheat the
inside of the thermos with hot water, according to the
care and use instructions for best results. If you are preparing a
thermos jar to fill with soup, pasta or any other hot food, you may
heat it in the microwave, before filling the jar,
or even in a radiator. Please be careful when
handling the hot contents. Remember that you are not heating the
food or beverage to eat it on the spot, but you are doing this
process in order to eat it safely hours later.