Louise's expert suggests using a much larger sleeve than the map but I suggest caution in that regard. I think you need to allow 1/4-1/2 inch gap between the tape and the paper map but much wider than that may result in the map slipping around inside the sleeve and getting damaged (edges and/or print).
Here's a document that tells how to encapsulate a map.
https://www.nps.gov/museum/publications/conserveogram/13-03.pdf
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www.nps.gov
July 1993 Polyester Encapsulation Polyester encapsulation is a way of sandwiching a paper object between two pieces of stiff, chemically inert, clear plastic.
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Angie
Sent: Thursday, April 19, 2018 12:07 PM
To: [log in to unmask]
Subject: Re: [MAPS-L] Tape for Mylaring a map?
Hello all,
Here are some thoughts from one of our preservation staff at UCLA.
--Louise
Ideally Mylar encapsulations should be welded with either heat or an ultrasonic welder. Tape is just not ideal as tape adhesive tends to leach out a little around the edges of the tape over time. If the University of Northern Iowa does not have access to an ultrasonic welder or a heat welder, and they must use tape, this is the kind of double-sided that’s typically used, and it would be the ¼” wide tape:
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www.gaylord.com
3M 415 Polyester Double-Sided Tape (36 yds.) features a high-tack acrylic adhesive that won't dry up, crack or yellow. The tape is ideal for encapsulation and making special enclosures and mounts.
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If at all possible, I would recommend having a much larger mylar sleeve than the map itself, leaving as much margin between the map and the taped edge of the mylar encapsulation to minimize potential contact of map to leached adhesive.
From: Maps-L: Map Librarians, etc. [mailto:[log in to unmask]]
On Behalf Of Susan Moore
Sent: Wednesday, April 18, 2018 2:21 PM
To:
[log in to unmask]
Subject: Tape for Mylaring a map?
Greetings!
We ahve a map that we would like to encapsulate in Mylar. We've got the Mylar that has been handed down from map librarians past put we don't have any way of sealing the Mylar. At one point, they apparently used some type of double-sided tape. Since this is a map from the 1890s, I'd like to do right by it. What tape, if any, should we use to seal the Mylar. (And yes, I'll leave some sections unsealed to allow for off-gassing.)
Susan Moore
University of Northern Iowa
Cedar Falls, IA 50614