Brazing & Soldering
Brazing and soldering join metal by melting a filler metal, without melting the parts themselves. Plumbers sweat copper pipe, HVAC techs braze refrigerant lines, and electronics workers solder circuit boards. The flame and heat start fires, and the filler metals and fluxes can give off harmful fumes.
- Plumbing
- HVAC
- Electronics
Soldering vs. brazing
- Soldering uses filler metals that melt below 840°F (450°C).
- Brazing uses filler metals that melt above 840°F, so it needs hotter torches, often oxy-acetylene or air-acetylene.
Fire: the biggest hazard
Sweating pipes inside walls and ceilings has burned down many homes and buildings. The fire can smolder inside the wall for hours after you leave.
- Get a hot work permit where required. See Hot Work Permits.
- Put a flame-protection cloth or heat shield behind the joint.
- Wet down nearby wood framing if it’s safe to do so.
- Keep a fire extinguisher or water within reach.
- Stay and watch after you finish, and check the area again before leaving. Many sites require a fire watch of at least 30 minutes, and some require longer. Feel walls for heat and sniff for smoke.
See Sparks & Fire Risk and Propane.
Fumes
- Cadmium: some silver brazing alloys contain cadmium. Its fumes can cause serious lung damage and cancer. Use cadmium-free alloys whenever possible, and check the label and safety data sheet.
- Flux fumes: many brazing fluxes contain fluorides that irritate the eyes, nose and lungs.
- Rosin (colophony) fumes from electronics solder flux can cause asthma. Use fume extractors at soldering benches.
- Keep your head out of the fume plume and use local exhaust or ventilation, especially in tight spaces.
Lead solder
Lead solder is banned for drinking water pipes but is still used in some electronics and other work. Lead mostly gets into your body from your hands, not from fumes at soldering temperatures.
- Don’t eat, drink, smoke or vape at the bench.
- Wash your hands well before breaks and before going home.
- See Lead.
Burns
- Joints stay hot long after they stop glowing. Treat all metal as hot.
- Use soldering iron holders, and never grab a falling iron.
- Wear safety glasses. Flux and molten solder can spatter.
- Brazing torches need shaded eye protection. Shade 3 or 4 lenses are typical for torch brazing.
Torch work checklist
- Hot work permit, if required
- Heat shield behind the joint; combustibles moved or protected
- Extinguisher or water within reach
- Cadmium-free filler metal; ventilation for flux fumes
- Fire watch after finishing, and a final check before leaving
Standards & references
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