What substance is recommended for cleaning surfaces before brazing?

Acetone is highly recommended for cleaning surfaces before brazing due to its excellent ability to remove grease, oil, and other contaminants that could interfere with the brazing process. Proper cleaning is crucial, as any residue on the metal surfaces can lead to poor adhesion and weak joints. Acetone evaporates quickly, leaving no residue behind, which is ideal for preparing metal surfaces.

Other options, while they may clean surfaces to some extent, do not provide the same level of effectiveness. For example, alcohol can leave behind moisture or residues that might not be optimal for brazing, while water can cause rust or corrosion on the metal surfaces, leading to further complications. Oil, on the other hand, is not suitable for cleaning prior to brazing since it introduces grease that must be avoided to ensure a good bond. Thus, acetone stands out as the best choice for preparing surfaces before the brazing process.