Vintage (looking) metals have become increasingly popular in jewelry making. The process of giving metal a vintage or antique look is variously called darkening, oxidizing, patinizing or antiquing.
Brass is the most common metal to undergo antiquing in jewelry making.
There are various ways to create antique brass which can be done at home. (You can also find out how to antique copper).
For you to be able to oxidize the brass so that you can quickly achieve a rich aged patina on the metal, raw brass must be used. However most brass components come with some protective varnish. And grease (like from fingers during handling) is also deposited on the surface. These must be removed thoroughly before the antiquing process begins.
Clean brass component completely with any of the following:
Here is a collection of various methods that you can try out. Experiment with the various antiquing metals to discover your own favourite.
Suspend your brass items over ammonia that is in a covered jar, making sure that the brass components do not come into contact with the ammonia. You can use fishing line or nylon stocking to suspend the metal. Secure it to the bottle with rubber band or sticky tape on the outside. Then lid the jar.
This can take a few hours. Check on progress and determine when you are satisfied with the color changes.
Soaking brass in Clorox (toilet bowl cleaner) will help dull the brightness and tone down the brassy, shinny tone without leaving a brown patina on brass.
Brush the brass items with saltwater. This is slower than brushing with vinegar but it produces a different patina - possibly a more "antiqued" look.
Brush or vinegar over the entire surface of the brass items. Allow to dry and check results. Reapply and dry repeatedly till you get the patina colour you want. This method should give you a quick darkening of the brass.
Suspend the brass items over vinegar and allow the fumes to oxidize the brass. You can suspend the items using nylon stocking, cheesecloth, or fishing lines over the vinegar (not in it). Cover the entire setup with a bucket or other container to prevent the fumes from escaping.
This is a list of products that I have heard are good for antiquing brass.
Patina Green Antiquing Solution (from company Moden Options) - can be used on copper, brass, bronze. For both indoors and outdoors. No special tools required. Water based.
After the antiquing process, you can allow the brass to age/oxidize naturally. Or you can (temporarily) seal the antique finish using beeswax. Prepared beeswax like Johnson's Wax can be applied directly using a clean. lint-free soft cloth.
You can also try floor wax or a clearcoat.