Aging copper for the Arts and Crafts look
Giving copper the old look
Over the years craftsmen have used various treatments to give new copper an old look. One old method, still employed by some artisans today, involves bathing the copper in a solution made by dissolving chunks of liver of sulfur (potassium sulfide) in water. But this process poses a hazard. "Potassium sulfide hydrolyzes in water, releasing hydrogen sulfide (H2S), a gas as toxic as the hydrogen cyanide used in a gas chamber," warns Dr. Jim Lindberg, professor of chemistry at Drake University. "Without adequate ventilation, it will kill you," the chemist says.
The thought that aging copper this way might suddenly stop our own aging led us to try some other methods. In tests, we achieved best results with another chemical -- rapid fixer, a common photographic material. Camera shops usually sell rapid fixer, or you can check the Yellow Pages for photographic-supply retailers. (We bought a 16-ounce bottle of Ilford Universal Rapid Fixer. Kodak and others market a similar product.)
Cleaning the copper is the first order of business. To remove oils and dirt, scrub both sides with kitchen cleanser. Rinse well.
Then, sand the exposed face to a satin sheen, using a fine (red) Scotchbrite pad followed by an ultrafine (gray) one. Don't make fingerprints on the copper -- wear gloves or hold the piece with clean rags. (We wore latex medical gloves throughout the operation and handled the copper by the edges.) Wash off the sanding residue. (We swabbed it off with denatured alcohol.)
Dilute the rapid fixer 1:2 with water. To do this, pour a measured amount of fixer into a clean two-liter pop bottle (or similar suitable container), and then add twice that amount of water. Stir or shake to mix.
Pour about 1" of dilute fixer into a suitable glass or plastic tray. (We bought a plastic photo-developing tray for $3.95 at the camera store where we bought the rapid fixer.) Slip the copper face-up into the chemical. Rock the tray gently to keep the solution moving across the copper's surface, as shown below.
After a few minutes, the surface will begin to darken. Continue agitating until the copper takes on roughly the color of cinnamon. (Reaching this final shade can take 10 minutes or so.) Don't let the color get too dark -- that hides the copper look.
Rinse both sides under running water, and then stand the piece on edge to air dry. You can help it along with a hair dryer or heat gun, but don't rub the surface. After the copper dries, check the color. If you've hit one you like, spray on clear gloss lacquer or acrylic coating.
You can reimmerse the metal to darken it. To lighten it, though, you'll have to sand to bright metal and start over again.
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