Glass Lined Vacuum Flask – 5 Features to Look For

Glass lined flasks are our greatest buddy in the chilly winters and scorching summers. These vacuum flasks keep liquids at a steady temperature. For example, if we pour hot coffee in the flask and seal it, it will remain hot for a long time and similarly, chilled lemonade will stay cool for longer duration if kept in a vacuum flask. But why would we want hot or cold drinks on the go? The thing is that we humans are warm blooded beings and we need to keep our body temperature regulated at nearly 37 degree Celsius. This is the reason why we crave for hot beverages when the outside temperature is below our desired level. Hot drinks help us maintain and increase our body heat in cold temperatures. And this also works in the reverse; when we feel hot, we like to drink cold beverages to lower our body heat.

What are Vacuum Flasks?

Vacuum flasks are also called Dewar bottles or thermos. They are insulated bottles that keep the contents inside at a stable temperature for a long duration of time, irrespective of the surrounding weather conditions. It was invented in the year 1892 by Sir James Dewar and consists of two flasks. One flask is placed inside the other and the air is partly removed from the space between the flasks, generating a near-vacuum, which checks on the heat transfer by conduction or convection.

How do Vacuum Flasks Work?

What will happen if you take a glass of chilled ice tea or a cup of steaming hot coffee and keep them out on the kitchen table? While your coffee will cool down, the ice tea will warm up to the room temperature. This is because if you place any two items with dissimilar temperatures, then the heat transfer will occur and result in both the items to reach the same temperature. Basically vacuum flasks prevent this heat transfer through the walls of the thermos flask.

Five Features of Vacuum Flask to Look Out For

1.  Silver Interiors

You must have noticed a glass casing inside all your vacuum flasks ( This casing is very fragile. It is surrounded by a vacuum and is protected with an outer plastic or metal casing. Usually, you can unscrew and take out this glass envelope for cleaning purposes. Moreover, to decrease infrared radiation, this glass casing is also silvered like a mirror. This entire arrangement of a vacuum and the silver interiors diminishes the heat transfer to a great extent.

2.  Vacuum

Vacuum means the complete absence of atoms in an area. While it is impossible to achieve a complete vacuum, but by removing a major part of air between the two compartments of the thermos, an almost vacuum can be attained. In the absence of these atoms, heat transfer through conduction and convection can be totally eliminated.

3.  Insulated Support

Sometimes large quantities of liquid needs to be stored for temperature maintenance and for this a large and long vacuum flask is used. However, these huge flasks cannot hold the inner container completely just from the neck alone. To solve this and provide better stability, additional supports called spacers are placed between the interior and exterior casing. These spacers also work as a thermal conduit and partly decrease the insulation of the thermos around the region where these spacers link to the interior shell.

4.  Cap

While the walls and bottom of the flask offer proper insulation and prevent heat transfer, the neck or the opening of the thermos does not offer any vacuum. This can affect the temperature of the contents in the flask. To minimize this, a cap or screw-on stopper is used to block the air flow and also to prevent the contents from spilling.

5.  Outer Casing

Though the outer material of the thermos does not play a major role in its insulation effect, but it is still a very critical feature of the glass lined flask. It is very essential that the outer shell of the thermos is made of high grade plastic or metal; otherwise it might crack and shatter unexpectedly. Moreover, the outer casing comes in various colors and designs and you can choose the one that suits your personality and taste.

So, keep these features in mind and go ahead and buy some great glass lined vacuum flasks to beat the heat or treat the winters this season!