We buy ready-made mylar pockets, in 8 or so standard sizes. These have one open side on one of the long edges.
Probably a tad more expensive than buying a large roll of mylar, but saves a lot of time/effort in making pockets ourselves.

We do not seal up maps entirely because 

- we will eventually want to digitise it

- may need to conduct preservation work / analysis on the original map now or in the future. 

- patrons often want to photograph a portion of a map (rather than buy a scan of the whole thing from us) and the mylar has too much reflection/glare for this to work well when still in the pocket.

- because we pencil call numbers on the map itself (except for rare material), we sometimes need to change the number as a result of discovering related material elsewhere in the collection.

- we may want to put the material on display in our exhibition galleries.


Brendan Whyte
National Library of Australia