At some point, copper trim was added to the kitchen. It lined the rafters, the edge of the counter and covered some light switches. Evan removed it all before working on the ceiling and walls. The copper was completely covered in grease. Removing it proved to be quite difficult because I couldn't put force on it since it is so thin and delicate. I scrubbed each piece with white vinegar and salt using a sponge and steel wool.
It took much longer than I thought it would and didn't turn out quite as well as I had hoped, but nonetheless the copper trim is looking much better.