If you just put a print into a frame without a mat or spacers contact with the glass can cause sticking buckling newton rings and a variety of other problems.
Framing a print without a mat.
Like a mat floating gives the piece some space.
Most framing experts agree that it is best to keep the pastel surface away from the glass.
Second we use a spacer to create space between the plexiglass and the surface of your work.
If there is a border around the image that border will be visible unless you cover it with a mat or cut it down and get a smaller frame.
For this reason i use a spacer when framing mat less.
The trick is to use spacers to create an air gap between the print and glazing glass or acrylic.
Picture frames destination inc.
When matting is eliminated the framing options are to either sandwich the painting against the glass an old french method or to utilize a spacer.