Digital BW, The Print

I have been told by an expert in paper longevity that lignin, perhaps the
primary acid reserve in wood-pulp based paper, is photo sensitive, turning
brown when exposed to UV light.  While there are sophisticated tests for
lignin (and one is going to be run on EAM), this expert suggested just
exposing paper to UV or sunlight to see if it contains lignin.  So, I
decided to see what would happen to a variety of papers if I simply placed
the papers with the paper backs almost touching a 15W UV fluorescent "black
light."

For the test, I selected papers from newspaper to the cotton papers.
Because Eclipse is coated and optically brightened on both sides, I included
one that I'd torn off the coating to be able to measure the cotton interior.

The short summary of results is that the newsprint turned brownish in a day,
whereas the other papers show almost no change after 100 hours.

(The newspaper, by the way, tests out as neutral with the acid test pen,
whereas the back of EAM tests as acidic.  I have omitted the one day results
for the "good" papers because there was no significant change.)

The yellowing that I did observe in some of the "better" papers seems most
likely to be optical brighteners in the paper base burning out and turning
yellow, although I don't know why a premium paper manufacturer would put
those brighteners in the paper base of a coated inkjet paper.  (Xerox does
put them into it's premium multipurpose paper, but that paper is not
coated.)  So, I don't think the yellowing of the allegedly premium papers
means much.  But, who knows?

It appears that UV bleaches at least some paper slightly.  As such, it might
be that looking at the relative numbers is most telling -- that is, what
happened to the yellow reading relative to the other readings. I assume that
yellowing of the paper is not a good sign.

Museo, the cotton paper with no brighteners, lost a unit of yellow, as did
the interior of the Eclipse Satine cotton paper -- as also did EAM.  These
are the only papers to show this pattern.

The detailed readings of the X-Rite are as follows (in order of C/M/Y/Visual
density, and the decimal point is omitted):

		Control 		One day UV		105 hours of UV

Newsprint	21/21/24/21		18/25/39/21		16/26/42/21

Xerox Premium Multipurpose
 paper	7/7/6/7					6/6/6/6

EAM		4/4/6/4					4/4/5/4

Eclipse	2/3/0/2					2/3/4/3

Eclipse
  inside	3/4/5/3					3/4/4/3

PhotoRag	3/4/3/4					3/4/4/3

LPM		4/4/2/4					3/4/5/4

Museo		2/3/4/3					2/3/3/2


Because there was so little change in this test, I went back and measured
the backs of the EAM that has been subject to the longest fade test I've
conducted -- 1200 hours of exposure to a fluorescent light.  These are the
results of that test:

EAM control: 4/5/7/5;    EAM back after 1200 hr: 4/5/7/4.

My visual impression is that the 1200 hour test strip paper had yellowed
just a hair.

The longest non-EAM test I've done is with Hahnemuhle German Etching.  That
test went 500 hours.  Here are the readings of the backs of the control and
test strips for that paper:

German Etching control:  3/3/4/3;  500 hour test:  3/4/5/3.

Wilhelm allegedly rated EAM at only 30 years due to a poor paper aging test.
I don't know what test he used, but what I see most using is a high
temperature (90 C) test with humidity at 50 RH.  The presence of water
(humidity) is needed for acidity to have an effect.  So, my rather crude
test here for lignin is not necessarily contrary to what Wilhelm found.
There clearly is some acid in the EAM paper backing.  However, my test for
lignin shows no evidence of significant amounts of it in EAM.

Paul
http://www.PaulRoark.com