Copper patina problems

A. Hi Lisa.
You'd probably have to name a stature and provide a pic for a more definitive answer, but buildings, roofs, and statues with blue/green verdigris patinas are probably just old and natural. Certainly artwork might be waxed or clear coated. Flame coloring is primarily interference coloring from burnt oil to my understanding and would not be expected to be durable, nor to retain good coloration under a wax or clearcoat.
Luck & Regards,


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

A. Jeff, it is likely your tubing is alloy C12200 which contains phosphorus. When applying muriatic (hydrochloric) acid, you would get a smut (coating) formed. I am guessing your patina process, like most, uses mixed, mildly acidic chlorides, or oxides that react with the copper surface, and develop a green color when dry. Perhaps a smut prevents the patina reaction by inhibiting the surface. I would try a dip in 10% nitric acid, to get a bright copper surface, (like a new US penny), rinse with deionized water, then apply the patination solution. Do not allow surface to dry off between steps. If this fails, you may need to use copper tubing that is unalloyed, such as C10200.

A. 50% vinegar [in bulk on eBay or Amazon]. I put my copper pipes (from the hardware store) that have been cleaned with steel wool, in a five gallon bucket and spray, spray, spray. I turn the pipes about half way thru the process. I also use copper wire and caps on my garden sculptures so they are also in the bucket. I let them dry between spraying. I can get a beautiful patina overnight! I finish with a rub of linseed oil to preserve the patina. Beautiful results!

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Ed. note: Thanks for the idea and the pictures, Teri!

A. Remove the patina using a weak solution of sulfuric acid (10 %) and re use your patina solution more diluted . Or try to put on some wax on your patina. The wax will darken the patina .

A. Hello Linda,
It is probably possible to create a smooth, consistent color and clear coat it for durability. But if you are letting bare copper be exposed to the conditions of a bathroom sink, spots and dullness must be expected. You need to choose, not expect bare copper not to spot :-)
Luck & Regards,


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

A. Hi Mike. I don't think it can be done without clearcoating. The blue-green coloration is quite soluble and non wear resistant. Pennies resting quietly between boardwalk slats are blue-green, whereas pennies in circulation always turn brown, not green-blue, because the blue-green has no wear resistance.

Regards,

A. Hi Mike. There are excellent books about patinas, such as "The Colouring, Bronzing & Patination of Metals" [adv: this book on eBay, Amazon, AbeBooks] . But if you are not an artist, buying a commercial patinating solution such as Jax or Modern Options sounds more promising. I'd try spraying a two-component automotive clearcoat on after the patinating because, as I say, those blue green tones are highly soluble salts (you've probably seen the staining of concrete below most copper, brass, and bronze outdoor items).

Regards,