Archival Conservation Questions and Answers
Document Repair Tape and Mending Tissue:

Quesion: I recently bought a roll of Document Repair Tape to use to cover some tearing on pages of a book. Do I apply the tape to both sides of the paper, or to just one side? If both, should I try to fold the tape over (continuous) or use two strips?
Answer: Less is more. If you can get away with applying the Document Repair Tape or Transparent Mending Tissue that you have on just one side of the tear, that should be sufficient. For poster repairs and like items, the tape should be applied to the back to allow the image (in the front) to be free from the tape. For books and like items that have works or images on both sides, you’ll just have to make a choice.