A bubble leak test is a simple but effective method of finding refrigerant leaks by spraying a specialized, high-viscosity soap solution on copper joints and valves. If there is a leak, the escaping gas will create a cluster of bubbles, pinpointing the exact location of the hole. While electronic leak detectors are great for finding "general" areas of a leak, the bubble test is the definitive way to confirm the spot before brazing. This solution is designed not to corrode the copper or damage the insulation over time. It is a "must-have" consumable for any service technician's tool bag.