Analysis
Analysis
To understand an object, it helps to take it apart in your mind. In this section we look at what a familiar object consists of, what job each part does and how materials behave over years of use. These breakdowns do not replace instructions or tell you what to choose: they help you see how a thing is made.
A vacuum flask keeps things hot not because it heats them, but because it barely lets heat escape. That is the whole trick.
Inside an object: how a vacuum flask works
Two walls instead of one
The heart of the flask is an inner vessel with two walls, one set inside the other, with a narrow gap left between them.
This is exactly the kind of double-walled vessel James Dewar proposed in 1892.
A vacuum in the gap
The air has been pumped out of the space between the walls. Without air, almost no heat passes from one wall to the other.
Reflective surfaces
The walls of the inner vessel are usually made shiny so that they reflect radiant heat back inside instead of letting it out.
A narrow neck
The narrower the neck, the smaller the area through which heat escapes. That is why a flask's neck is noticeably narrower than its body.
Stopper and cap
The most vulnerable point is the top. The stopper blocks the path of warm air, and the cap often doubles as a cup.
Outer casing
The casing protects the fragile inner vessel from knocks and gives a comfortable grip. Its material and shape can often hint at the object's approximate period.
Materials of ordinary things
| Material | Strengths | How it ages |
|---|---|---|
| Wood | Warm to the touch, easy to work and repair. | Darkens, cracks when it dries out, absorbs smells and moisture. |
| Tinplate | Light, cheap to produce, takes printing and paint well. | Rusts at folds and scratches; paint wears off over time. |
| Stainless steel | Strong, does not rust in normal conditions, easy to clean. | Picks up fine scratches and dulls, but lasts for decades. |
| Aluminium | Very light and a good conductor of heat. | Dents, darkens and develops a matt film. |
| Plastic | Can take any shape or colour and weighs almost nothing. | Fades in sunlight, turns brittle, may yellow and crack. |
| Glass | Does not absorb smells, does not alter the taste of its contents, transparent. | Barely ages, but breaks and gradually gathers a web of scratches. |
Read next
- Vacuum flask (in Russian)
Archived address note: how a laboratory vessel of 1892 became the household vacuum flask.
- History
A timeline of ordinary things: Dewar's vessel of 1892, the 1899 torch, stainless steel in 1913, the wheeled suitcase and blue LEDs.
- People
Inventors, designers, craftspeople, curators, restorers and collectors: the roles that together make up the culture of things.
- Collections
Three reading routes: light at home, things for the road and kitchen utensils.
- Articles
Six magazine topics, from the history of household things to collecting, plus a catalogue of articles written for English-language readers.
Sources
- Encyclopaedic sources on the history of technology and materials science
- Patent offices: specifications of patents for household inventions
Dates of inventions and patents are taken from open historical and encyclopaedic sources. Exhibition, fair and museum lecture schedules change, so always check them with the organisers.