Capacity
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.
Flask material
The material from which the flask is made is the inner container of the thermos, which usually comes into direct contact with the product inside. Among the most popular modern materials are
stainless steel,
glass,
plastic and ceramics; here are their main features:
—
— Glass. The main advantage of glass over stainless steel is complete chemical inertness: such flasks do not oxidize and do not acquire an unpleasant odour over time. This makes them perfect for products where flavor matters a lot, such as herbal blends. In addition, this material retains heat better. On the other hand, the strength of glass is significantly lower, and such thermoses are...rather poorly suited for hiking — mostly glass flasks are placed in models that are not designed for difficult conditions.
— Plastic. This material is characterized by low cost and relatively low thermal conductivity (which helps to retain heat). On the other hand, the plastic surface does not tolerate prolonged contact with hot liquids: it can release unpleasant odours or even harmful substances. Thus, plastic flasks are relatively rare — mainly in thermos mugs, which, by definition, are not designed for long-term storage of hot drinks, as well as in inexpensive food thermoses.
— Ceramics. A material that is in many ways similar to glass: ceramics do not react with the contents of a thermos, do not affect its taste and smell, but are afraid of strong blows. At the same time, the reliability of this material is somewhat higher than that of glass — on the other hand, ceramics are more expensive. Therefore, this option has not received much distribution.Material
The material from which the body is made is the outer part of the thermos, inside of which the flask is placed.
—
Plastic. One of the main advantages of this material is its low cost. In addition, it can be given any colour, and low thermal conductivity contributes to better temperature retention. On the other hand, plastic cases are noticeably inferior to steel cases in terms of strength and reliability, and scratches easily appear on their surface, due to which the product loses its presentation as it wears out. Therefore, plastic is used mainly in inexpensive models of thermoses.
—
Stainless steel. Steel is somewhat more expensive than plastic, but much stronger and more reliable. In addition, the steel surface has a stylish appearance that is long-lasting thanks to its scratch resistance. Among the shortcomings of this material, in addition to the price, high thermal conductivity can be noted; manufacturers usually compensate for this moment with various tricks that further increase the price. Nevertheless, in general, steel is a very favorable material in terms of price and quality, and it is from it that the cases in most modern thermoses are made.
