These paints are water based and contain real metal particles. They will tarnish naturally over time and when exposed to the elements.
But, if you are impatient like me, you can get the activator solution and apply it over the wet paint, and have the effect within 20 to 30 minutes.
The activator will react with the real metal particles in the paints, thus speeding up the oxidation process.
So, this is what I did with it....
Don't know what you call those "indent" thingies, but I rusted mine. :)
You get a protective coat to apply over the oxidized metal finish, minimizing any further corrosion, and to create a weather resistant barrier, but I found that it darkened the color, and made it look less natural, so I'm taking my chances.
The more common use for it is on outdoor plant containers and ornaments, like this:
I got this generic plant container at a garage sale for two dollars, and transformed it into something I love.
Again, I want it to go on rusting and tarnishing over time, so I did not put a top coat on.