How To Stretch Watercolor Paper With Masking Tape. Staple one corner of the paper to the board. Let the sheet dry overnight.
Get your paper lined up straight on your board, and tape each side. The paper will need to be wetted repeatedly and turned over to ensure the entire surface is adequately soaked. Once the paper is dry, it will be stretched tight on the board and will not warp when watercolor is added.
Finally dry the paper using a hairdryer !
Make sure there’s no air trapped under the paper. This kind of tape is water activated. If the paper is too wet, blot it with a clean sponge and if the tape is too dry, simply run a damp sponge over it. Gently run your fingers around the edge to make sure all the air bubbles are removed but trying not to stretch the tape.