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Green flame tips when annealing


I watched a video by Charles Lewton-Brain, for ACAD, where he demonstrates annealing (bare copper sheet, no barrier flux) and shows how the flame turns a bright orange when annealing temperature has been reached.

I decided to try this out myself, on sterling silver sheet, using Pripps Flux.

In this instance, the flame turned a bright green, just before the flux went from powdery to glassy, and a millisecond before the flux started to turn rust brown color (similar to how the Borax cone flux turns rusty brown when soldering temperature is approaching.

If I stop at this point, my metal is soft.

If I stop before this point, my metal is not soft.

Has anyone else experienced this green flame? I am wondering if it is a color indication, similar to the one Charles Lewton-Brain demonstrates, which in his case is orange.

1 Like

Interesting. Thanks for the video.
If I have a large piece or I’m having trouble getting a piece evenly annealed I turn out the lights to see the color of my metal. Some of my professors made sure we knew and used primitive techniques. :face_with_monocle:

Thinking out loud + I see a green flame with copper. &Wonder… if the copper in your sterling could have caused it ??? Could the copper have burn out, fumed and causing the green flame color? I think, Maybe.

My first thought is that the Borax in your flux caused the green flame.
If you try to recreate your test without flux that may help with an answer.

Safety Data Sheet Prip’s Soldering Flux Grobet