When brazing copper to copper, how can you visually identify that the copper is at the correct temperature?

When brazing copper to copper, visually identifying that the metal has reached the correct temperature is crucial for achieving a strong and durable joint. The correct indication is when the copper turns a dull red color. At this temperature, typically around 1100°F (593°C), the copper has reached a state where it is adequately heated for the filler metal to flow and create a strong bond without overheating and damaging the copper.

The dull red color is a key indicator because, at this stage, the metal is not glowing excessively, which would signify overheating, and it is also not too cool, which would prevent proper brazing. Keeping a careful eye on this color transformation allows the technician to maintain control over the brazing process, ensuring the integrity of the joint.

Other choices may provide misleading indicators of temperature. For instance, bright yellow suggests the metal is overheated and could potentially degrade the copper. Shiny surfaces could indicate that the metal is heated but are not a reliable guide for the correct brazing temperature. Emitting smoke generally indicates that some materials or coatings might be burning, which could compromise the brazing process. Therefore, recognizing the dull red color is essential for effective and reliable brazing of copper components.