Silver solder, sometimes called hard solder, makes strong joints on copper, brass, bronze and steel. The solder itself contains 20 to 40 per cent silver and other alloys to ensure strong bonds for various applications and environmental conditions. Silver soldering requires more heat than soft soldering, up to 466 degrees Celsius. The areas to be soldered must be impeccably clean of dirt, corrosion, oil or grease. Always flow the solder onto the joint and never try to melt it into place with the torch. And make sure the items fit closely together. Silver solder will not fill gaps.
- Skill level:
Things you need
- Emery cloth
- Wire brush
- Soldering torch
- Silver solder
- Clean rag
Use an emery cloth, wire brush and solvent to clean away all dirt, corrosion, oil or grease from the surfaces. Try to make the surfaces shine, as the solder adheres best to bare metal.
Clamp or wire your pieces together so that they don’t move around while you solder.
Coat the areas to be soldered with flux. Mix it with water, if necessary, to form a paste and spread it evenly over the areas you will solder.
Slowly heat the elements you are soldering with the torch. Be careful not to blow away the flux. Heat the junction slowly at first until the flux gets hot, and then concentrate the heat onto the joint.
Touch the solder to the heated joint and let it flow onto it. If the solder doesn’t flow, the joint is not hot enough. When the joint is hot enough, the flux should look glassy.
Allow the joint to cool. You can immerse it in water to speed up the cooling process.
Tips and warnings
- The scale that forms as the joint cools can be cleaned off with emery paper. You can also soak it in citric acid. Remove any stains from the acid with emery paper, and then you can prime and paint it if you want.
- Remember that the steel will get very hot and could scorch or burn anything it touches. Keep a bucket of water, or even a fire extinguisher handy.
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