Digital BW, The Print

----- Original Message -----
From: "Paul Roark" <paul.roark@...>
To: "DigitalB&WPrint" <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Monday, September 23, 2002 8:35 AM
Subject: [Digital BW] Deacidification -- It's not just for EAM


> There is an excellent and reasonable current summary of information
related
> to paper preservation at:
>
> http://www.clir.org/pubs/reports/pub95/contents.html
>
> The article is called, "Preservation Science Survey --
> An Overview of Recent Developments in Research on the Conservation of
> Selected Analog Library and Archival Materials" written is December 2000
and
> published in cooperation with the European Commission on Preservation and
> Access.  Chapter 2 is devoted to paper.
>
> One interesting note seems to say that even "acid free" paper will not
stay
> that way long. The article notes, in part:
>
> "Formation of acids"
>
> "While it is well known that papers become more acid with age, it is
> generally assumed that this declining pH does not significantly contribute
> to the degradation of paper. It is often presumed that only the acids
> introduced in the manufacture of paper and those absorbed from the
> environment are responsible for the deterioration of paper. In this
context,
> the term "acid-free," which in effect equates neutral and alkaline papers,
> is often used to imply permanence. However, the spontaneous formation of
> acids in cellulose during aging cannot be overlooked as a cause of paper
> degradation."

Paul,

A good link to have. As you may have noticed they have not mentioned lignon
anywhere. It is the lignin in cellulose derived papers that decomposes to
produce weak acids. That is why it is important that un-buffer papers be
both acid free and lignin free with as little sulpher content as possible.
For more in depth information check out the Stanford site:

http://palimpsest.stanford.edu/
http://palimpsest.stanford.edu/byauth/misc/dirsci.html#lc
>
> ...
>
> "[N]eutral papers cannot remain acid-free for long. Weak acids formed in
the
> degradation of cellulose and hemicelluloses have generally been considered
> not to pose as significant a threat as do stronger acids introduced from
> acidic alum-rosin size or those formed by absorption of oxides of nitrogen
> and sulfur from the environment. However, the present findings suggest
that
> these weak acids accumulate at a sufficiently high rate to contribute
> significantly to the increasing acidity in paper as it ages. Alkaline
papers
> showed appreciably higher [Is this a typo?-PR] rates of accumulation than
> did other papers, since the acids formed are immediately neutralized and
> cannot enter into other reactions or dissipate.

Sort of. Chemical weak reactions such as this are often bidirectional and if
the reaction products are being removed then the reaction will continue
rather than stabilizing. It might be more appropriate to substitute
"generation" or "formation" for "accumulation". Since the acids are removed
they cannot harm the paper.

> It was also shown that these
> weak acids attach themselves strongly enough to paper, probably by
hydrogen
> bonding, that they are not easily dislodged from the paper matrix, even
upon
> airing. Because of this tenacity and because they catalyze their own
> formation, these acids present a constantly escalating source of damage
that
> can be dealt with only through deacidification."

Good un-buffered papers need to be made from quality alpha cellulose, and be
both acid-free and lignin-free. Paper permanence is not image permanence.
You have often seen in your fade tests that EAM did better than other
papers. Most recently on the PiezoTone tests compared to Photo Rag which is
alkaline buffered. While alkaline buffering is good for paper life, we don't
know if it is good for ink life.

Martin Wesley

http://www.borderless-photos.de/guests.html