Digital BW, The Print

I previously noted, "The Abbey acid test pen makes just as yellow (acidic)
marks on the back of the old fiber prints as it does on Epson Enhanced
Matte."

I have done some further experiments that lead me to believe the fiber paper
in silver prints is much better than EEM.

I took the old fiber print that tested as acid as well as the EEM test strip
and de-acidified them with ammonia gas.  After this they both tested
alkaline.

Starting with no acids, the question was how soon lignin in the paper would
produce acids that would show up as yellow with the test pen.  The test
prints were left hanging in the air to avoid any contact with acidic
materials.

The EEM started to show yellow (acid) in just a few hours.

It has now been a few days, and the fiber print is not showing any yellow.
It quickly lost the purple alkaline results, but the color has stayed what
I'd call neutral.  The test results look just like the highly-respected,
pure cotton Arches paper test results.

So, I conclude that the paper used in the Kodak fiber-based silver print I
tested is very good with very little if any lignin in it.  The acids I found
probably came from surrounding materials.  While not in contact with acidic
papers, the fiber prints were in a metal file drawer that also did have some
acidic papers in it.  The lesson may be to store prints in buffered boxes --
which is the standard recommendations for B&W prints, I believe.  I suspect
buffered interleaving would also be a good move for B&W (not color, as I
understand it).  Even acidic papers in the same file drawer may be a source
of danger to silver prints.

Paul
www.PaulRoark.com 
___________________________________



-----Original Message-----
From: Paul Roark [mailto:paul.roark@...] 
Sent: Friday, March 05, 2004 8:32 PM
To: DigitalB&WPrint
Subject: [Digital BW] Acidic Silver Prints?

I just read that the paper used in making traditional photo fiber-based
prints is actually purified wood pulp.  Lignin in wood is the main reason it
has a tendency to become acidic even if no acids were used in processing.
Cotton has no lignin, which is the hard substance that allows trees to be
tall.  Thus cotton - almost pure cellulose - is considered a much better
(but more expensive) base for paper.

 

I've heard that while lignin can be reduced substantially in wood-based
papers, it can never be 100% removed.  So, for archival wood-based paper,
the trick is to reduce the lignin to less than 1% and then have 2% buffer
(usually calcium carbonate) in the paper to offset the residual lignin as it
breaks down and forms acids.   The buffers absorb the acids before they can
do any damage to the cellulose.

 

Unfortunately, wet prints that go through an acid stop bath can't have
buffers, it appears.

 

(I've heard that a small amount of residual fix left in the print actually
helps preserve the print.  Is this because it can act as a buffer?)

 

I've also heard that the air &/or airborne gases or pollutants can cause an
acidic cascade in even pure cellulose, cotton paper unless it is buffered.

 

So, it occurred to me to test some of my old fiber-based silver prints that
had never been mounted.

 

I hate to say it, but the Abbey acid test pen makes just as yellow (acidic)
marks on the back of the old fiber prints as it does on Epson Enhanced
Matte.

 

(Most of my silver prints are mounted on buffered mat board.  Hopefully the
buffered mount board is helping to absorb some of the acids.  I'm going to
be looking for buffered interleaving sheets for the rest.)

 

I wonder if an EEM print with a buffer sprayed on the back or mounted on
buffered board would last as long as an Ansel Adams print?  It now seems
like a much closer question than I would have guessed.

 

Paul

www.PaulRoark.com <http://www.paulroark.com/>  



[Non-text portions of this message have been removed]



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