I have an old set of antlers that was my grandfather's that I would like to mount up. The skull plate cracked in half sometime within the last 40 years and someone in the family duct taped them together and threw them in a box. They have great color because they have been in storage and I want to keep them that way. I washed them with warm water but I cant get the tape residue off. I'm scared to use solvents because I don't want to discolor the them. Any suggestions?