Obtaining flame colors on copper

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I am torch cutting .040 thick copper,resulting in, a black red oxide coating. I can clean this back to orginal copper color with a solution of vinager and salt. My question is how can I obtain rainbow type colors on clean copper. I have read about controlled heat method but don't know what temp.and time is required. I have tried flame torching with little success. The result being very little color variation.

Thanks for your help.

Sam Gonnella
hobbyist - Pueblo, Colorado, U.S.A

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Ref a book dissolve 4g caustic +fine sugar 4g in 100g water.boil for 15 minutes, and while stirring add ,slowly, 4g copper sulfate solution. Immersing in hot solution will create coloring rainbow from gold to green to black.

Cair Shishani
aircraft maintenance - Al Ain, United Arab Emirates

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October , 2008

Hi, Sam. Several examples are shown and a good discussion of the subject is available on letter 2662. Good luck with it!

Regards,

Ted Mooney, P.E. RET finishing.com Brick, New Jersey