Mylar Encapsulation Question

[Shayla]

Hi. When you encapsulate a paper item in mylar, how do
you make sure it won't slip from it's position behind the mat
window? Does static between the mylar hold it in position?
What I've seen says to have the 3M 889 tape about a quarter inch away from the edge of the paper.

In this case, there's one piece of paper about 6x8" in one
window, with another tinier one about 3/4 by 2" below it with
it's own window. It's a replacement from an earlier job and the
dimensions need to be maintained. There are a lot of them in a display case, and they have to be exactly the size they were before. There's only about 1/2 an inch between the two windows. The outside of the mat is an inch and a half or less.

 

[Jim Miller]

An encapsulation mount holds a paper item in three ways:

1. All clear polyester film has a curvature. Placing the sheets' convex sides together creates slight mechanical pressure in the center of the mount.

2. The static charge of the polyester film helps hold a paper item in position.

3. When strips of a thin-profile, double-sided tape such as 3M#889 are positioned within 1/4" of the paper item's edges, it creates a pinching action that keeps the item from moving within the mount, because the tape is thinner than the paper. A thicker tape such as ATG would not create the pinching action. If the tape lines are placed beyond 1/4" the pinching action diminishes. If the tape lines are placed closer than 1/8", it is more difficult to cover them with a window mat and still show the edges of the item. Also, the clear film sheets would tend to pull apart, and the mount would be more difficult to assemble without the tape contacting the item.