No two ways about it, getting a good black patina on zinc came can be a problem. But it is not impossible. I sometimes tell my students that the best thing about using zinc on their project, is that it will probably disappear inside their project’s wood frame, but that doesn’t have to be the case. Follow these few simple steps and you’ll find that, with a few modifications to standard patina finishing procedure, getting a nice dark finish on zinc isn’t such a mystery after all. You won’t be able to get a copper sulfate finish on zinc; the chemicals just won’t work, but you can get a number of shades from light charcoal to black
Step One: Metal Prep
Zinc fresh out of the case, like any other metal, will immediately begin to oxidize. You may not be able to see any visible signs of oxidation, but believe me, it’s there. To combat oxidation in preparation for applying any patina to your zinc, you should first go over the metal surface with a fine grade steel wool (000 or 0000 grade will work just fine. See photo top left). As you do this, you will notice a difference in the finish of the zinc (See photos right). Compare the freshly cleaned areas of your zinc came with untouched areas and you will see a noticeable difference in color and shine. The cleaned zinc came will be a lighter silver in color and will have a brighter sheen on its surface. Your zinc is now ready for patina.
Step Two: Clean The Metal
This is simple, but necessary. Be sure to wipe your metal surfaces clean of any residual steel wool filings. They will only get in the way of your patina and create little rust spots if they are left on the metal. Rinsing won’t hurt either, but a good wiping with a damp paper towel or shop rag will do the trick.
Step Three: Apply the Patina:
Amazingly, you can sometimes get a very nice black finsh on zinc using copper sulfate patina, depending on the specific brand you use. Or you can just rely on black patina to do the job. The important thing to remember is that it will take a number of coats to get the job done. You can apply the patina solution with a brush or paper towel; make sure you cover all of the metal surface you wish to darken. Inevitably, your fisrt coat will look terrible (See photo left), but that’s normal. Once the first coat is applied, remove any excess patina solution form the metal.
Step Four: Second Coat
Before you apply the second coat of patina to your zinc came, you must remove the first coat. This is easily done with your fine grade steel wool. Clean the metal as if you were preparing it for patina. Once all of the darkened areas of the zinc are removed, clean as above and apply a second coat of patina. Your second coat should look fine (See photo right). If not, just repeat the process. In most cases, two applications will suffice, but sometimes imperfections will still be visible and an additional coat may be necessary. In that case, just repeat the cleaning/application process. Your final result should be completely dark with no blotchy or bare areas.
Step Five: Polish
You can enhance your finish by applying a coat of paste wax to the metal surfaces (See photo bottom right). Just wipe the wax on, wait a few minutes and buff to a shine.
There you have it: A nice dark patina on zinc came. Enjoy.
This post courtesy of Joe Porcelli of Glass Craftsman Magazine