Here is a great book.
The Colouring, Bronzing and Patination of Metals
It has gorgeous pictures, and detailed descriptions of the processes required for a number of finishes. My folks got it when try were doing some diy copper trim. Turned out decently.
The Colouring, Bronzing and Patination of Metals by Richard Hughes and Michael Rowe is quite useful.
It might have been this one . It’s been a while. Haha
Reference books are always handy, though!
Sorry about the measurements saw the gallon part and figured you were on this side of the ocean. I was thinking about how specifically vague ounce/sq foot really is without context as I was making breakfast. And thanks to all the responses I can maintain my arbitrary yank based measurement system unscathed
Anyway... Patina.
Yes you can force a patina and you should be well aware of the fact that it is a chemical reaction whether it occurs naturally or not. Via this process certain disgusting and potentially plant killing things can leech out or simply be washed around and put into the soil. Its not something I would recommend but I'm also kind of up tight about that stuff so I'm not the best judge to go by but you should check around and find out what patinas are really doing before you dump some on your prize winning whatevers
That said there are a ton of recipes and techniques that can be used to color copper. From very simple ammonia fuming(which I don't like very much) to something like rokusho which is made with radishes(very specific radishes but yeah radishes) to metal penetrating dyes.
The biggest issue is more about how much chem lab you want to create and are comfortable working with. If you were in the states I would point to a company that I've had good luck with but since most formulas are acids or corrosives the shipping to you would be measured in fuck tons.
I would be surprised if there wasn't someone in your neck of the woods that does patinas but you may need to be the resourceful one.
This book... Is expensive but you may be able to find a copy of it somewhere to look through http://www.amazon.com/The-Colouring-Bronzing-Patination-Metals/dp/0823007626. It is a remarkable piece of shop literature and has more or less all of the ways to color copper and bronze.
Not sure this is the one you want but it is the top if the line and so you may be able to find something a few rungs down the ladder from it and have good results since most other books have pinched their 'own' recipes out of it.
Hope it helps and good luck.