As is the case with most home improvement jobs, the key to successful copper pipe soldering is proper preparation. If you take the time to acquire the right supplies, your work will be faster and more effective.
Use a propane torch for heating the joint--these torches come in self-igniting and manual-lighting models. In either case, open the fuel-adjustment valve just before igniting the propane.
Use a wire-handled striker to ignite manual models--matches are less reliable and more dangerous. You will also need some liquid tinning flux to prepare the joint for soldering and to remove any oxidation.
The flux can be applied with a small paintbrush. Use a tube cutter (available in any plumbing supply store) to quickly and easily cut small copper pipes, and an emery cloth to clean the joint before adding the flux.
Finally, protect yourself with goggles, heavy gloves, and a heavy, long-sleeved shirt.
Preparing the Joint
To cut 1-inch pipes or smaller, a tube cutter will do the job cleanly and easily (larger pipes can be cut with a hacksaw). Remove the burr from the inside of the freshly cut pipes with the reaming attachment on the tube cutter, and then clean the pipe end (inside and out) with the emery cloth, being careful not to touch the cleaned pipe with your bare fingers.
The oils from your skin will contaminate the metal, compromising the quality of the join. Paint a small amount of liquid flux on both pieces of pipe to be joined, using a small disposable paintbrush.
Fit the pipe ends together firmly, and unroll a section of solder wire--a 6-inch piece should be sufficient. Hold the spool of solder wire with one gloved hand, with the tip of the wire against the joint.
Heating the Joint
To ignite your propane torch, simply open the fuel-adjustment valve and spark the striker (for manual ignition) or press the ignition button (for automatic ignition). Adjust the flame so that the narrow blue cone in the center of the flame is about 1 1/4 inches long.
Since the tip of this blue cone is the hottest part of the flame, apply this part of the flame to the joint. Apply the flame to the fitting, rather than to the pipe itself, since this is where the metal is thickest.
Keep the flame moving in a gentle back-and-forth motion. While you are heating the fitting, keep the solder wire tip on the side of the joint opposite the flame.
When the metal is hot enough, the solder will melt and flow into the joint. As the solder melts into the joint, move the torch and the solder wire around the joint until the solder has melted into the entire circumference of the fitting.