Tarnish, verdigris and patina are all different ways that make metal (and other materials) look old. In some cases, the oxidization process takes years, in others, months.
Tarnishing refers mostly to silver, especially sterling.
Old silver eventually obtains a muted opaque look, generally with darker areas where the wearing isn’t removing the tarnish.
Really good silver will tarnish beautifully; as the years pass, the patina will only improve.
Verdigris is the greenish blue that occurs on brass and copper, as well as bronze, the admixture of the two metals.
Used for statues commemorating heroes, as roof panels for some very famous buildings, and as the metal used for the Statue of Liberty, the verdigris that shows after years of weathering is very different from the original gleaming colour of copper kettles and brasses used on horse tack.
Verdigris is almost impossible to fake. If ever the verdigris is removed from a roof for instance, or copper rain chains, it can never be matched.
You can make copper wire oxidize enough to get some verdigris by spraying it with a strong vinegar solution, and after several sprayings it will start to change colour.
Use pickling vinegar, for a safe method of making verdigris. See more about verdigris here.
Muriatic acid will also work, but requires more care as it is very strong. It's used as a rust remover in commercial applications, and can be purchased at vehicle maintenance supply stores.
Patina is a catch all phrase to mean the look of age or weathering that occurs to all items.
It can be the lichen on old buildings and bridges, unchanged for centuries, or the look of a well loved piece of antique furniture.
Once removed by renovation, the patina will never be the same.
Coin collectors know this all too well – after the first time someone brings them a valuable seldom struck piece of ancient currency that they 'cleaned up' – removing the patina purposely is never a good idea, as it removes the worth and value of the piece too.
Rusting is another way to make metal look old, and fortunately, it is possible to fake.
Only old farm equipment and cars left out in the baking sun for decades can beat the faux rusting process that I use.
Simply throwing cans and metal objects, even shiny new barbed wire into the fire to remove any paint or other manufacturing finishes, and then leaving the item out in the rain and weather to finish the process can give you a beautiful rusty patina.
You can speed up the process by spraying with bleach which will make the item rust almost instantly. Rinse the bleach off when it’s done its job.
You need to take care when handling these items, as the rust will come off on your hands.
Once you finish making the craft you can lightly rub it with some kind of oil to give it the ability to withstand wear.
Try out these ways of making metal look old, and create some patina on your rustic crafts.
Punched Tin Lamp Shade