Any advice on methods to age metal items?
Thanks,
Dr.Cyclops

Air, water, heat, acids, salts, sandpaper/emery cloth...a really good paint job.

Take your pick.

Cheers!

In the past I have left some of mine outside in the garden for a couple of weeks! - Very authentic but unfortunately, you have little control over just how much ageing you are going to get!

Here's some interesting information:

Aging Metal

All those aging recipes work fine, but you can also ask a theatrical painter. Patina can be painted very convincingly. The real advantage is that the material your spectators suppose the item maybe is not used for the construction. You can use paper mache, plaster, wood or plastics and the paint job will make it look like marble, solid iron, precious hardwood or else. For shop decoration, there exist some colours especially for such purposes; for instance: paint that immediately looks like rust.

The other reason to use a good paint job to represent aging is there is less potential danger of a treated or stressed metal part failing prematurely. Many illusions call for the support of weight in one way or another. You don't want to take any chances with structural integrity.

All are very useful ideas. I have had really good results for aging tin, iron etc., with liquid drano and rock salt. PM for details.