1. Properties of flashlight flames

There is a common, albeit incorrect, terminology:

• a plumber "soldering" copper pipes to install a bathroom sink;

• an electronic circuit manufacturer "soldering" components onto a printed circuit board;

• a metal furniture company "welds" steel tubes to make chairs, stools and so on.

In all these examples, the verb to weld means: to establish metallic continuity between two or more originally separate parts. But :

• the plumber performs soft (tin) or hard (silver or copper-phosphorus eutectic) soldering;

• printed circuit board components are fixed by tin soldering;

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