The nominal volume of a thermos is the maximum amount of contents that it can be guaranteed to contain.
This parameter is directly related to the type (see above). So, a capacity
of up to 500 mL is quite normal for a thermo mug, a flask or a baby thermos, but it is considered small for a classic thermos, and even more so a jug or a thermos for food. The
"500 to 1000 mL" category includes most traditional and food models; for mugs, flasks and children's thermoses, this is actually the maximum volume. Among the jugs there are many more capacious options —
from 1000 to 1500 mL. A volume
of 1500 to 2000 mL is considered quite large, and the most solid models can hold
more than 2 liters.
Anyway, a large volume allows you to hold more drink or food, but the downside of this is an increase in the size, weight and price of the thermos itself. Therefore, when choosing, you should not chase the maximum capacity, but proceed from real needs. For example, a model of 400 – 500 mL is quite enough for two cups of coffee, and for tea drinking at a halt for 3 – 4 people, it is advisable to have a model of at least 1000 mL. More detailed selection recommendations can be found in special sources; especially they will be useful to those who choose a thermos for long-distance hiking trips.
The main property of a thermos is to maintain the temperature of the liquid poured into it. Accordingly, the key parameter of efficiency is not so much the case material or some of its heat-insulating marketing chips, but the value of the water temperature after a certain period of time. So manufacturers, confident in the quality of their products, are happy to share their achievements. The temperature value after 6 hours shows how many degrees the boiling water poured into the thermos (98 °C) will cool down at an ambient temperature of about 20 °. And values of more than 80 ° can be considered very worthy.
