🫗 Vacuum flask

A vacuum flask is a container that keeps a drink hot or cold for a long time. It consists of two flasks, one inside the other, sealed at the neck, with a partial vacuum between them that insulates the contents. A silvered coating on the outside reduces heat loss.

The vacuum flask was invented by the Scottish scientist James Dewar in 1892 to hold liquefied gases at very low temperatures. He never patented it. In 1904 the Thermos company, set up by two German glassblowers, patented the flask, gave it that name and brought it to market, recognising that it could keep liquids warm as well as cold.

Warm milk for a baby should not be kept in a flask for long. Prepared infant formula gives bacteria ideal conditions to grow, so WHO advises preparing each feed fresh and discarding any feed not consumed within two hours of preparation, unless it was refrigerated. When away from home, the feed can be prepared at the destination using hot water of no less than 70 °C.