----------------------------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 [log in to unmask]