Step 6 · Heat the Joint
Unroll about 8-10 inches of lead-free solder from its spool and bend the end into a 90-degree hook for easy application. Using a torch striker or lighter, ignite your propane torch and adjust the flame so you have a distinct, bright blue inner cone about 1-2 inches long. Begin heating the joint, focusing the tip of the blue inner flame on the middle of the copper fitting, not on the pipe itself. Move the flame back and forth across the fitting to heat it evenly. The goal is to heat the fitting, which will then transfer its heat to the pipe inside it. The joint is hot enough when the flux begins to smoke or bubble. You can test the temperature by briefly touching the solder to the joint on the side opposite the flame; if the solder melts instantly on contact, the joint is ready.