Flux can also act as a temperature indicator, minimizing the chance of overheating the parts. Handy Flux, for example, becomes completely clear and active at 1100°F/593°C. At this temperature, it looks like water and reveals the bright metal surface underneath—telling you that the base metal is just about hot enough to metal the brazing filler metal.
Temperature
|
Appearance of flux
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212°F (100°C)
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Water boils off. |
600°F (315°C)
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Flux becomes white and slightly puffy, and starts to "work."
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800°F (425°C)
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Flux lies against surface and has a milky appearance.
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1100°F (593°C)
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Flux is completely clear and active, looks like water. Bright metal surface is visible underneath. At this point, test the temperature by touching brazing filler metal to base metal. If brazing filler metal melts, assembly is at proper temperature for brazing.
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