----------------------------Original message----------------------------
In the past year I've noticed that many American libraries
encapsulate maps to prevent wear and tear from users. Maybe the
following is of interest to you.
 
The Royal Library of The Netherlands has executed "An orientating
investigation into the influence of encapsulation on paper with
artificial aging".
 
The materials investigated were:
Melinex 400 (75 micron)
Lexan (250 micron)
Secol (50 micron)
 
Samples were:
Ragpaper (printed, 1813 [year], woodfree)
VGF document (Dutch document paper, 80g/m2, woodfree, alkaline
paper)
Sheets from a book of 1892 (printed, containing wood)
Sheets from a pocketbook from the 50s (printed, containing wood)
Journal-paper (printed, containing wood, The Guardian, appr. 4
months old).
 
Some samples were deacidificated by putting
methoxymagnesiummethylcarbonate (MMMC) in freon/methanol (Wei T'o
soft spray) on one side of the paper.
 
Total aging-time was 138 h. with a 6 h. cycle alternating between
50 degree C / 35% Relative humidity and 90 degree C / 80%
Relative humidity.
 
Results
Some folies change their outlook. Secol is usually a little
bumpy, Lexan is slightly warped. Melinex doesn't change in
outlook.
Secol doesn't have a lower tear-resistance, with Melinex it
decreases significantly. Lexan was too thick to measure.
The difference in outlook and tear-resistance might be resulting
from their thicknesses.
 
Samples were tested on tear-resistance (T) folding (fold-number =
F) and colour (C). "0" = no significant change; "+" =
significantly better; "-" = significantly worse.
The results are shown in the following table.
 
Paper         variable       influence of       influence deaci-
                               sealing          dification and
                                                sealing
------------------------------------------------------------------
 
ragpaper         T                0                    0
                 C                0                    +
 
VGF-document     F                0                    0
                 T                0                    0
                 C                0                    -
 
19th c. paper    T                0                    0
                 C                +                    0
 
1932             T                -                    0
                 C                +                    0
 
pocket-book      F                -                    -
                 T                -                    0
                 C                +                    0
 
The Guardian     F                0                    0
                 T                0                    0
                 C                +                    -
 
 
There are some conclusions, but they are varying to whether
papers are deacidificated or not.
 
The final conclusions is:
"Seen the results it is recommended to be reserved when using
seals of synthetic material foliate for conservation of paper.
However this investigation has been directed to the "contents' of
the seals. Even when paper in seals deteriorates faster than when
they would no be encapsulated, the whole of paper AND
encapsulation will be many times stronger and easier to handle
than loose sheets of paper.
 
The investigation was done by Sophia Pauk (chemical analyst) and
Dr. Henck Porck (conservation scientist) of the Department for
Library Research of the Royal Library.
 
Jan Smits
Mapcurator Royal Library, the National Library of The Netherlands
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