Snippage (...) I've worked with the stained glass tape in the manufacture of stained glass before and you can blacken the finish with a patina. try this link: (URL) the foil can be seen here: (URL) (20 years ago, 8-Oct-04, to lugnet.parts.custom, lugnet.trains)
(...) The patina is an acid of sorts that reacts with the copper. Not sure of the end result would be to conductivity. I imagine it would be reduced some but not totally impeded. Mike (20 years ago, 8-Oct-04, to lugnet.parts.custom, lugnet.trains)