This is the most critical step for a successful joint. First, use a deburring tool (often a triangular blade attached to the tubing cutter) to ream the inside of the cut pipe, removing the small lip or burr created during cutting. This ensures unrestricted water flow. Next, use a specialized pipe cleaning brush (or fitting brush) to clean the inside of the copper fitting until the surface is bright and shiny. Then, use sand cloth or a dedicated pipe cleaning tool to scour the outside of the pipe end (about 1 inch) until it is also bright, shiny, and free of any oxidation or dirt. Do not touch the cleaned surfaces with your bare hands, as skin oils can interfere with the soldering process.