How to ADD a black patina to a bare aluminum frying cauldre I was born in 1936 and my mother bought a small aluminum ( 6.5 inches in diameter ) cauldre, thus it is my own age, 75 years old. It had a beautifull black patina on the outside and to make a long story short, somebody in my family found it and removed all this patina and painted some ridicolous flowers on it. To do this the patina was removed ( maybe with sandpaper ). Now this item is again in my posesion and I removed the ridicolous flowers and now the small cauldre is shining aluminum color. 
I would like to ADD a black patina on it, on the OUTSIDE. All the information there is on the Internet is about seasoning the metal on the inside.
Does somebody know how to do this ?
this is just my guess, but i would think that seasoning on the outside would be the same... like illustrated here at the Black Iron blog: http://blackirondude.blogspot.com/2009/01/easy-cast-iron-skillet-reconditioning.html