Digital BW, The Print

Short version:

 

We may be able to make any glossy paper - also known as RC or "barrier"
papers - "acid free" and perhaps archival by spraying the back with Wei T'o
deacidification spray.  (See http://www.weito.com/intro.htm)  

 

Long version:

 

The Epson premium glossy papers are rated by Wilhelm as having a dark
storage life of ">200" years, just like the best cotton papers.   Most
glossy papers are not rated so highly.  When I test the Epson premium papers
for acidity with my Abbey acid test pen, the difference I see is that the
interior fibers are alkaline - buffered paper.  The interior papers of all
other glossy papers I've tested are acidic - not buffered.  It is typically
the acids from lignin that limit paper life.  That is why EEM is not rated
very highly - the paper doesn't last as long as the image.

 

It appears that the Wei T'o deacidification spray penetrates the back side
of these papers and buffers the interior fibers, but is stopped by the resin
(polyethylene) barrier from reaching the surface. 

 

One of the problems with the deacidification sprays is balancing the goal of
buffering the paper fibers with the conflicting desire to not touch the
surface of the print and pigments.  The buffers may lessen the dmax and
might cause the image to yellow faster with light exposure.   

 

One type of deacidification spray (Bookkeeper by Preservation Technologies)
does not penetrate paper at all.  If the paper is sprayed on the back, this
protects the image, but it also does not get the buffer into the paper where
the lignin acid source is.  (Bookkeeper just puts little magnesium oxide
particles on the back of the paper as if they were pigments.)  The theory of
Bookkeeper is that acids migrate enough to be mopped up by buffers that are
close.  However, in my tests on EEM the interior papers never did stop
testing as acidic.

 

Another type of deacidification spray - Wei T'o - has the buffer (magnesium
carbonate) dissolved in a solvent.  With this spray the buffer is pulled
into the paper by the solvent (alcohol and some others), where it can be
more effective.  Wei T'o makes different versions of the spray with
different solvents that carry the buffer differing distances into the paper.
I have #12, which carries the buffer into the thickest papers.

 

The problem with this approach on matte papers is that the solvent carries
the buffer right up into the inkjet coating and image.  In fade testing I
detected more yellowing in the test strip sprayed with Wei T'o than in a
control test strip.  The principal of Wei T'o has also warned that the
coatings could be complex systems where the effects of the buffer might be
unpredictable.  We probably just do not want the buffer to get into the
coating and image.

 

So, what about glossy, "barrier" papers?  Will the Wei T'o penetrate the
back of the paper but be stopped by the RC barrier?  

 

It appears that many if not most inkjet RC papers have the resin -
polyethylene - just between the coating and the paper base - unlike
photographic RC papers that have polyethylene on both sides of the paper.  I
noticed with the roll of Glossy Paper Heavyweight I was testing that a spray
of water on the back would take the curl out of it.  This would not happen
if the back were polyethylene.  Since the barrier is to stop the water in
the ink from reaching the paper base, and these prints are not processed in
a tray of water like photographic RC papers, it does make sense that only
one side would need a barrier.

 

I have now tried the Wei T'o spray on the backs of several glossy papers,
including Epson Glossy Photo paper and Ilford Galerie Smooth Pearl.  These
are two of my favorite cheap glossy papers, but they have acidic paper
interiors that will limit their lives.

 

The Wei T'o does penetrate the backs of the glossy papers I've tried.  With
the 2 papers above, the interior fibers tested as very alkaline after
spraying, just like the Epson Premium glossy papers.

 

But, with the Epson Glossy Photo Paper, I could not tell if the Wei T'o had
also penetrated the barrier and polluted the surface.  This is because the
Glossy Photo paper has an alkaline surface to start with.

 

The Ilford Pearl, however, like the Epson Premium papers, has an acidic
surface.  (This correlates with a higher dmax.)  So, if the Wei T'o
penetrated the barrier, it would turn the surface alkaline - It did not.
Thus, the Ilford paper may have been effectively buffered without the
coating and image being affected because the polyethylene barrier kept the
Wei T'o in the paper and away from the coating.

 

In short, the Wei T'o spray may make the cheap and good looking glossy
papers acid free.  This could extend their lives very significantly (many
times).  I'll have to fade test some samples as soon as my current test is
over (which will be more than a month from now).

 

This could be rather significant - cheap, acid-free glossy paper.   The
Epson Glossy Photo paper is even bronzing free.  Now if we could just find a
thicker version of that .

 

Paul

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



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