When choosing framing materials for your artwork, you can either use ready-made or custom frames. You might select a wood or metal frame, or even one made of recycled materials. Whatever you choose, you need to buy archival-quality framing materials to go with it. Specifically, any foam core backing boards, mats, or framing squares or strips should be archival quality and acid free.
EXPERT TIP: Try Lineco See-Thru Polyester Mounting Strips. You can cut them to size, and if you place one strip on each side, they will securely hold the watercolor paper in place. Consider placing the mounting strips directly onto the back of the mat. If you place the strips on the mat, rather than the backing board, then even if the mat slips inside the frame the watercolor paper will always move with it, rather than falling out of position when jostled. You can further protect your work by using acid-free frame-sealing tape.
If you buy a custom frame, don’t forget to get hanger hooks and an appropriate wire that is designed to hold the weight of the frame plus the artwork.