Soldering is a method of joining various metal items by melting and flowing a filler substance (usually metal) into the joint–the filler has to have a melting point that is lower than that of the materials it is joining.
Soldering is different from welding because you’re not melting the base metals during the joining process, and it’s not the same as brazing because you’re using a filler metal with a lower melting point. When you solder, the heat that’s applied causes the solder to melt and get drawn into the joint by “capillary action” (the pores in the metal suck up the solder) and to bond to the materials that you’re
|joining by “wetting action” (molecular-level adhesive forces that cause a liquid to adhere to and spread out on a solid surface). After the metal joints have cooled off and you’re done, the solder-based joint that you’ll have won’t be as strong as the base metal, but, if you’ve done it properly, it should have the necessary|
water-tightness, electrical conductivity, and strength for just about anything you would practically want it to do. Soldering has been around forever, much longer than gas-torch welding, and there’s even evidence that it was used up to 5000 years ago in Mesopotamia.
Now, something else you need to know before you solder anything copper is that because copper is an extraordinarily good conductor of heat as well as electricity, large copper items such as pipes and fittings need a lot
|more heat to properly solder than what a soldering gun or iron can do. Your best bet for most plumbing jobs is either a propane or MAPP gas torch, although some pros prefer acetylene for large jobs because of the higher heat (note: they don’t use oxygen with the acetylene like you would if you were|
welding–oxygen would make the flame much too hot for soldering and would likely melt the copper).
Before we get started, you need to remember that all the parts you’re going to join need to be clean and oxide (rust) free, and wire brushes designed for internal and external cleaning are available for common pipe and fitting sizes. You can also just use some steel-wool, emery cloth, or sandpaper as he does in the video below. Alright, let’s kick this pig, here we go:
Additional Resources and Further Reading
Really good article on soldering copper pipe for beginners from Reader’s Digest, very nice.
Here’s some really nice step-by-step instructions with photos for each step from FineHomeBuilding.com