Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

Bluing or blackening brass

Current question and answers:

Q. Hi,

Do you have any experience with Patinas on brass? We use a patina (blue type solution), it's patinating purple not brown. Would you know why?

Cheers Daniel

January 2021
A. Hi Daniel. Not knowing what you are trying to patinate, what chemicals you are using for it, what method you're using (dip, spray, brush), and whether you have never succeeded before or you've been doing fine for years and this problem suddenly popped up, it hard to suggest much ...

But the purple color can be one of three things, a contaminant which produces a purple salt (and that sounds unlikely); a very thin patina which lets the Yellowish brass color enter into the equation, producing purple from yellow & blue; or a thin patina that is introducing a diffraction/interference coloration (a color which isn't really there as a pigment of any sort).

Please take your purple item and just patinate it a second time, and tell us what happens. I think it will turn brown. Good luck.

Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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Q. Hi,
I need tips on readily available solutions/gels, etc. for browning/blacking/bluing brass details please (from light brown to dark brown, black and gun blue)? Must provide reliable predictable and durable results. Or if there is a collection of well tried "recipes" available (a book, etc.) -- info on that would be most welcome? We are building fine mechanical designs.
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