hang up prints without foam or frame.

[KmH]

Since it's Kodak Endura paper that means it's likely a chromogenic print (C-print), not an inkjet of offset print.

Chromogenic print paper is light sensitive, and has a layered CMY emulsion one side. One layer is Cyan, one layer is Magenta, and one layer is Yellow. Chromogenic color print - Wikipedia, the free encyclopedia

The point is - that chromogenic paper is not very absorbant.

Knowing what kind of print you have helps you make decisions about maximizing the longevity of the print.