Aging copper for the Arts and Crafts look
Working with Copper
Copper almost seems to be a metal made for woodworkers. Its warm, rich color complements wood rather than fighting with it for our attention. And, copper, one of the first metals used by man, works easily.
These virtues gave copper widespread popularity during the Arts and Crafts movement early in this century. Arts and Crafts homes and furnishings, which stressed the beauty of natural materials and handwork, often combined copper and wood.
So, when we researched a clock project, we decided that the shiny, new copper on the face needed an aged look, as shown above. After some experimenting, we came up with a simple way to give copper that been-around-awhile look for projects in the Arts and Crafts style.
Working with copper Many crafts-supply stores sell copper sheets for handcrafting, or you can buy it from a metals dealer. Copper comes in scores of alloys, though, so tell the dealer you want a soft, malleable one that you can work by hand.
Mark your cutting lines on copper with a scratch awl or other scriber. Pencil marks don't show up well on metal, and markers usually make lines too wide for accurate work.
Use a straightedge with nonskid backing. (If you don't have one, put a strip of double-faced tape on the back of a ruler. Press it against your shirt sleeve a couple of times to reduce the tape's tack before starting the layout.) Scribe curved lines against a French curve or template, similarly skid-proofed. For complex layouts, adhere the pattern directly to the metal with spray adhesive.
Copper cuts easily. Common tin snips will readily handle straight cuts and gentle curves in sheet copper about 1⁄32 " thick or less. As you cut, don't close the snips all the way. Doing so crimps the metal's edge every time the jaw tips come together. Instead, keep the snips moving forward so the cutting takes place mostly at the back of the jaws.
You also can cut this soft, non-ferrous metal with a scrollsaw, bandsaw, or portable jigsaw. Back the metal with scrapwood at least 1⁄4 " thick for power sawing.
A no. 5 blade (.038x.015" with 16 teeth per inch) works fine for a few quick scrollsaw cuts. For serious copper sawing, go with a metal-piercing blade (24-48 teeth per inch), and lubricate it with beeswax. If you have a variable-speed saw, run it at a slow speed for metal cutting.
For the bandsaw or jigsaw, select a general-purpose or metal-cutting blade with 14 or more teeth per inch. If you're using the jigsaw, clamp the workpiece securely to the workbench, the cutting line overhanging the edge. Cover the saw's baseplate with masking tape to prevent scratching the copper.
Smooth and true cut edges by filing. For best results, clamp the metal between two pieces of scrapwood in a vise. Stand the metal's edge about 1⁄16 " above the wood, as shown, and draw a mill-cut bastard file along the edge.
Lay out and drill any required holes before finishing the metal. This way, you won't risk marring the finished surface.
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 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.
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.