Digital BW, The Print

Scott,

>... talking about silver gelatin photo prints ...
>You and I both seem to have evidence that acid in photo prints is not bad,
> nor is mounting them on acid board, nor storing them in an acid
>environment (sealed container full of acid mount boards). 

I disagree.  I think it is generally accepted that acid will eventually
destroy the paper; it's just a matter of time.  I have old prints from the
1800's that are on acidic board, and they are in bad shape; some have been
totally ruined. 

With inkjet prints there have been stories from Florida of very rapid
deterioration of Epson Enhanced Matte prints.  Presumably the heat and
humidity in Florida accelerates the acidic attack on the paper. 

If we want our old family photos to be available to future generations, we'd
be well advised to use acid-free materials.

One of the issues I've looked into is how to save old, acidic photos.  In
the library industry there has been a lot of work with de-acidification
procedures.  I have products from 2 of the primary companies -- Preservation
Technologies and Wei To.  Both have aerosol sprays that put a buffer onto or
into the acidic paper.  (They use versions of magnesium oxide instead of
calcium carbonate.)  

The Preservation Technologies product sprays little micron-size particles of
magnesium oxide onto the back surface of the print and is limited by the
amount of migration of the acids and thickness of the paper.  (These buffers
do not migrate.)  

The Wei To product has the buffer dissolved in a solution.  (They have
several different solutions that penetrate different amounts.)  As such, it
soaks into the paper and leaves the buffers closer to the source of the
problem -- usually lignin in the wood-based paper or cardboard.  The
weakness with this approach is that the buffer is strong and seems to
slightly yellow the image in my fade testing.    

So, neither procedure is perfect.  

I think if I had an important print that was dry mounted on acidic board I'd
first de-acidify it in a bag with ammonia for about 20 minutes.  Then I'd
use the Wei To product on the back and hope that the dry-mount tissue
stopped the product from reaching the print. 

Paul
www.PaulRoark.com 
_______________________________ 



--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul Roark"
<paul.roark@v...> 
wrote:
> Scott,
> 
> Air borne acid?  
> 
> That may not be technically correct, and I'm not a chemist.  However, my
> understanding is that acids are molecules that have, in effect, a loose H+
> ion.  That ion travels by latching onto other molecules, with water vapor
> being a primary "host"(?).
> 
> As a practical matter I've heard it said many times that acids "migrate."
> As such, the photos we want to last should not be stored near (even in the
> same file cabinet, apparently) acidic materials.
> 
> While the acids may not be affecting the image directly (yet), some of the
> acidic papers, like EEM, can have very short lives -- much shorter than
the




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