The mat should cover a little of each side if doing a window mat (only the outside border and it goes over the print) and that helps keep it flush along with photo corners
If mounting it just to the board or a float mount, where it is the print basically on a board and that is it, photo corners will suffice if under glass. Keep in mind the print may then touch the glass, which could be a problem in high humidity settings, or with cheapr glass. I have had no problems with a screen print touching glass over time, but digital prints can get stuck to the glass.
Use acid free boards/ mats so they do not transfer paper acids to your print causing yellowing
Comments
you can use these little photo triangle tab things from Michaels. Let me look for a link
https://www.michaels.com/canson-self-adhesive-photo-corners/M20005267.html
The mat should cover a little of each side if doing a window mat (only the outside border and it goes over the print) and that helps keep it flush along with photo corners
If mounting it just to the board or a float mount, where it is the print basically on a board and that is it, photo corners will suffice if under glass. Keep in mind the print may then touch the glass, which could be a problem in high humidity settings, or with cheapr glass. I have had no problems with a screen print touching glass over time, but digital prints can get stuck to the glass.
Use acid free boards/ mats so they do not transfer paper acids to your print causing yellowing
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