Raw copper is pretty easy to antique using stained glass and bronze art antiquing chemicals found at stained glass and art supply stores. The color varies with the method.
Antiqued copper finish on chain (and many findings) is a plating process that produces a little different color than the chemical methods used in other crafts.
You can see the antiqued copper chain available in 30 Yard spools at Rings & Things at Antiqued Copper Chain. We carry many other copper items. Get an over view of all the copper components at Copper Findings.
It's worth mentioning the "old school" home based antiquing method I used on filigree earrings 35 years ago:
You can get an antique look with a lacquer finish that leaves some dark pigment in the crevices. This is often done with filigree findings.It can be done crudely with black spray paint, allow to semi-dry, wipe off with a rag dipped in thinner.
Years ago I used to put a batch of filigree findings in a rock tumbler, spray in some cheap black spray paint, add 5 or 6 drops of paint thinner and tumble them for a few hours. I'd end up slightly dulled highlights and a lot of dark in the crevices. It didn't work on a smooth, high polished item as it was all highlight. But even on a shiny, smooth piece I'd get a little duller finish because a small amount of very thinned out black paint covered the whole item. Depending on your needs that might work for you.
Some people use a magic marker and acetone. See http://svallee.com/_wsn/page16.html (Her site has a lot of information about various antiquing methods, specifically for costume jewelry. Using Tarn-X, baking it in the oven, etc, etc. Spend a few minutes on her site and see if any will produce the effects you want.)
Solutions to give a patina to bronze statues available at some art supply stores.
Raw brass findings may have a thin coat of oil which prevents glues from adhering. ("Raw" means just that - stamped out from brass sheet on greasy punch presses. They are "rinsed" by being passed through a tray ot dry sawdust. At Rings & Things hand wash any charms that we notice are still greasy but every now and then, a batch may still need a little extra help.) For complete degreasing, wash in warm water with detergent, rinse well and dry with some agitation to prevent water spots. (Heat lamp, warm boxwood sawdust or similar methods speed drying.)
For a brighter finish , tumble polish with steel shot in a basic rock tumbler. With the shot and water use a burnishing compound that is formulated to prevent rust on the shot and give a bright finish. Rinse well and dry as above.)
Archived threads in the New Forum
http://cs.beadandbutton.com/beadingforumarchive/forums/t/10551.aspx
http://cs.beadandbutton.com/beadingforumarchive/forums/t/7442.aspx
http://cs.beadandbutton.com/beadingforumarchive/forums/t/10889.aspx
antiquing with LOS
http://cs.beadandbutton.com/beadingforumarchive/forums/p/42425/409483.aspx#409483
http://www.beadinghelpweb.com/basics/reference/oxidizingliverofsulfur.htm