Museums are focused on preservation. They want things to last for decades. With this kind of time frame in mind, it is vital to be aware that something as simple as the oils on your skin can cause an acceleration of deterioration. When mounting an item using a museum method, it must be in its own environment, not in contact with any corrosive materials.
There are a variety of ways to do this, such as gum tape, mylar clips, corner clips, and acid-free surfaces among others. However, the objective is the same: keeping an image in place without intruding on its current condition while ensuring it is not in contact with any surface that can cause permanent damage. Also, you never want any valuable image permanently fixed to another surface or in contact with any material that caries any pH value other than neutral (acid-free). This could destroy your image, both structurally and in terms of its value. For more information regarding acid and pH values, read the following section entitled “What does acid-free mean?”.