Dear Olive Tree:
I have the birth certificate from my grandmother dated 1900. It had been folded for years and when I opened it the paper came apart at the folds.
What could I use to piece it back together? I thought of Scotch tape but wanted to ask before I did anything.
Olive Tree Answer: Claudia, how wonderful that you have such a precious document! I guess you've realized that these papers should never be folded, because they will eventually come apart.
One school of thought is that to repair a torn or ripped document, you should use an archival, transparent document mending tape. Do not use cellophane (scotch) tape.
However, the Library of Congress disagrees and states "If a paper item becomes damaged, place it in a folder and contact a paper conservator, who can provide the treatment needed. Avoid using pressure-sensitive tapes (including those called "archival") as they can cause irreversible disfigurement, embrittlement of paper and alteration of inks.."
Personally I would immediately scan the document even though it is torn. Place it
gently together as best you can and scan it as a .tif file. That way you have at least preserved the important facts! Depending how important the document is to you, and how irreplaceable, only you can decide if you want to try the archival tape method or hire a conservator.
The Library of Congress has information on paper preservation