Mounting pictures to wooden plaques is a great way to preserve important memories. Adding a polyurethane coat can give those pictures the extra pizazz and flash you desire. When you add a polyurethane coat to the project, you protect the image by sealing it while adding gloss and depth to the final product. You can control the level of gloss and depth by monitoring the number of coats you apply.
Prepare the plaque surface by sanding it with 220-grit sand paper. The surface must be smooth and as flat as possible. When finished, remove all dust with a damp towel. Allow the surface to dry while you prepare the picture.
Apply a thin line of glue around the edges of the picture. Leave half an inch of space between the glue and the edge of the picture to allow for expansion. Apply two more thin lines of glue diagonally from corner to corner, creating an x-shaped pattern inside the perimeter line of glue. This will keep the picture flat when you apply the first coat of polyurethane.
Place the picture in the desired location. Press the picture securely to the plaque using a clean, soft towel. Allow the glue to dry for five minutes.
Apply the first coat of water-based polyurethane. Use a wide brush and apply the polyurethane in thin layers. Do not worry about lines or ridges that appear in the polyurethane, these will flatten out while drying.
Allow the plaque to dry for four to six hours. Sand the surface with 220-grit sand paper. Do not be intimidated by the dust created during this step; sanding between coats is essential to achieve a deep, glossy look.
Wipe away the dust created by sanding using a damp cloth. Dry the surface with a clean towel and let the plaque air dry for a few minutes.
Apply the second coat of polyurethane. Follow the above steps for each additional coat. The number or coats you apply will depend on your preference. Each coat will add depth and gloss. Typically three coats are sufficient, but if you would like to add some flair to your project, you can add more.
If you are worried about the glue holding the picture to the surface, place a heavy book on top of the picture and let the glue set for five minutes.