Rus, I haven't seen any replies to your post so I'll jump in.
Patination is typically the last step in fabrication, done after
everything else (except stones) is in place. Your soldering and
polishing must be complete because torch heat and the pickling that
follows will destroy or significantly change the patination.
So the next logical question from your piece's description is....
How do I only patina part of the piece?
There are a couple of answers to that one. First, some chemical
patinas will only affect certain metals. Ammonia-fume patina is a
great example of this -- it will affect copper strongly and quickly,
but silver and nickle silver won't be at all affected. Other patinas
will have different effects on different alloys. If you want a
particular section of your piece completely free from patina effect,
you can block it off with clear nail polish. Once the patination is
complete, you can remove the nail polish with acetone without
affecting the patina. Or, you can leave the nail polish in place as
a final protective coating, but be aware that it does tend to yellow
Finally, there are torch patinas, which are best used in cases where
you have more homogeneous metal composition. They work best on
copper and steel, but you can get some really interesting effects on
silver and bronze as well. You're still doing this as the last step
before setting stones, and you are NOT quenching or pickling
afterward unless you need to redo the patina (you can do it over and
over again until you get exactly what you want). The heat you use to
do it is very low (smallest torch tip) and gentle, and the process
should be slow to get the widest range of colors. Air cool
completely, then seal the metal with wax or clear-coat enamel to
prevent fading. Then set your stone and you're done.
Hope this helps!
Handcrafted and Unique Artisan Jewelry