A vacuum flask has a vacuum in a sealed double-walled container. This is to reduce heat loss or heat gain by

The walls of the double-walled container are coated with aluminium. This is designed to reduce heat loss or heat gained by

The stopper is usually made from plastic or cork. If hot liquid is placed in the container a stopper will reduce heat losses by

Modern vacuum flasks are made from double-walled steel containers instead of double-walled glass containers. The main reason for this change is to

A typical modern vacuum flask can keep ..