Digital BW, The Print

Acid doesn't seem to have been used for paper making until some time
  in the 19th century...Googling appears to support that. If you can
  cite a link to the contrary, please do. Older paper has deteriorated
  for a host of other reasons. 

  Use of wood pulp was relatively recent.. it required acid from 19th
  sometime until the late 20th..it's been eliminated in some "green"
  papers to reduce environmental damage. 
This is basically correct.  Until ca. 1840's most and the best papers were made of cotton.  Cotton was expensive to make paper from and so came the profession of the "rag picker" collecting used cotton clothing to be made into cotton  based paper.

The Kraft sulfite paper making process was invented in the 1840's (remembrance from graduate school as to actual date) allowing the commercial manufacture of paper from soft wood pulp.  This meant that great amounts of lignin were now included in the resulting paper.  The acid residues from the manufacturing process plus the deterioration prone lignin (which produces more acids itself) and even more complicated chemistry are the basis of the modern self destructing paper.

Through this time most fine art papers had either a high cotton fibre content or were 100% cotton so they usually did not suffer from the same problems.  Thus the sad situation where paper, books, etc. made before 1840 almost certainly look better now than 20 year old newspapers and pocket books which usually were made from the absolutely cheapest wood pulp paper with the least processing for life.

Those who have had the privilege of viewing very old works of art on paper or books should know that the modern concept of "white" paper is just that a modern concept involving bleaching with very nasty materials.  You will also have noticed that when you are viewing old books the color change deepens as you get to the edge of the paper.  This comes from handling and from deteriorating agents creeping in from the outside environment from the edge of the page when the book is closed.  This could be smoke, oils, perspiration, etc.

Cotton  itself will deteriorate but at a very much lower and slower rate.  Its degradative products are yellow brown in nature BUT are water soluble.  Thus old works of art and books made from cotton and which are badly yellowed can often be totally refreshed by selective washing techniques as long as the ink, pigments, etc. allow this.  Lignin containing paper is very hard to do this to and obtain the same clock resetting results.

I have been watching this thread with great interest and some trepidation.

The more that we digital printers and artists producing "born digital" art come to think in terms of permanence of the image and the image substrate and their components the more you tread the journey of the master artists of the classical and Renaissance periods.

You are going to have to examine absolutely every component of your art.  The least permanent and most prone to change aspect of it determines the "archivalness" of the entire work.  This extends to the use of "glop" as a final coating for the ink image and on through the protective coatings you employ to finish your work.

I suggest strongly that you look at the model developed over the centuries, rethink it in terms of your modern materials but follow the model.  

The time was that a painting or print purchaser demanded their money back when the painting or print obviously deteriorated and got it too.

The evolution of the digital art work will get there to.

Mark MacKenzie
Art Conservator & Wet Plate Photographer
Alcalde, New Mexico

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