Digital BW, The Print

Mantinieri wrote, in part:

> If you ever visited Italy, you probably noticed that any 
> church older than 100 years has a room where older documents, 
> often related to a Saint or to some religious activities, 
> are displayed. No matter how well those old documents are 
> conserved, usually behind thick glass and
> illuminated by controlled artificial light, they show signs of
> deterioration, at the very least with yellowing of the paper and
> deterioration of the structure of the medium. 

On the other hand, there are papers that are more than 500 years old 
that look pristine.  Museums like the Getty in L.A. have very old 
books with beautiful white pages and vivid images.

What accounts for some papers lasting many centuries and others 
deteriorating?  

The findings of one study group of experts looking at 
the "Composition and Condition of Naturally Aged European Papers," 
noted:

"... there is a belief that certain constituents such as gelatin 
content, pH, degree of beating, trace metal content, and fiber type 
may play important roles..."

The two factors that seemed to correlate well with good longevity 
that this group focused on most were: 

"... high pH values (pH = 7.0–9.9)...

"... sheets with high gelatin content (6–12%) all had high pH ..."

See http://aic.stanford.edu/meetings/abstracts/bpg_abstracts.html

(Scroll about 1/3 down the document to get to the "Composition and 
Condition of Naturally Aged European Papers" abstract.)

This seems to be consistent with the composition and reputation of, 
for example, the Arches Hot Press (un-coated) water color paper.



Paul
www.PaulRoark.com