.....
this is the Library of Congress and their specifications for archival
papers.  I would suggest clicking on the first option in the card stock
category.


http://lcweb.loc.gov/preserv/supply/specific.html.

Brief Summary of the specifications:  The stock must be free of optical
brightening agents, the pH, cold extract, range 8.0-9.5, and calcium
carbonate should be between 2 and 5% for Buffered papers and a pH of 7 
and
no CaCO3 for unbuffered papers.

these are some of the questions you all should be asking of the various
paper mfgs/distributors.

thanks for your attention
robert rex