I have read that older houses may have aluminum wiring, and to splice copper to it there is a less than desirable method of purple wire nuts using corrosion inhibitor paste.
My house was built in 1977, I had a home inspection done when I purchased the house a year ago that concluded that the house is copper wiring, and I read the sheathing for all of the wiring heading into the main breaker box and nothing seems to identify as an AL conductor, all standard copper Romex and the like.
All this to said, I was replacing nearly all of the fixtures, switches, outlets in the house and there were two places I backed off the wire nuts and found a sticky black paste on the twisted wires (dining room chandelier and outdoor porch lights). There wasn't any sheathing exposed to investigate further (and i didn't have the presence of mind to clean the bare wire enough to see if it looked aluminum). Am I being paranoid about the aluminum wiring thing? Would some electrician's opt to use some kind of conductive paste (black?) on a typical copper to copper termination? Or is there a chance that most of the visible working runs in the house we're replaced but maybe some aluminum was left some walls?
Thanks for any pointers, insight.