Step 1
Sand the copper sheets where the joining will take place with a sanding cloth to remove burrs, debris and oxidation. After sanding, the copper sheets will have a bright and shiny appearance.
Step 2
Place a copper sheet on a non-flammable work surface, secure in place with clamps, and put the second copper sheet in place where the two will join. Remove all flammable materials from the area to avoid a fire.
Step 3
Turn on an oxy-acetylene torch and heat the copper surface, keep the torch in constant motion to avoid reducing the copper to molten metal. Continue to move the oxy-acetylene torch back and forth until the copper is hot enough to melt the filler. The only way to determine the correct temperature is to keep to testing the flux or filler metal to see when it melts.
Step 4
Touch the hot copper sheet with specialized brazing filler metal made expressly for copper. The metal filler will melt and through capillary action will cover the heated area and join the copper sheets.
Step 5
Allow the copper sheet to cool completely and use a sanding cloth to rub away excess filler gently.