How can items be soldered without a soldering iron?

Question

How can items be soldered without a soldering iron?

Answer 1

With a propane torch, solder, and flux.  That's how plumbers sweat joints on copper pipes.

Answer 2

The original soldering irons were heavy and were kept in a fire until you wanted to use them.

There is infrared soldering with either high intensity light or IR lasers

Answer 3

i saw someone put the thing that want to be solder on a hotplate and use just the solder. But not saying to try it tho.

Answer 4

It depends on the application. Plumbing typically is performed using a torch instead of a soldering iron. There is also induction soldering. Electronics are often soldered using wave soldering.