None of the above
None of the above.
Cleaning the outside of the pipe
Cleaning the inside of the pipe
Cleaning the outside of the fitting
Cleaning the inside of the fitting
At least 1/4"
Half the diameter of the tubing
All the way until it "bottoms out" inside the fitting
The solder melts when it touches the joint
The copper glows bright red
The flux bubbles and hisses
You can no longer hold the pipe with your hand