Wood veneer is a common material used to cover plywood, medium-density fiberboard (MDF) and other low-quality solid wood substrates. Veneer is a thin sheet of solid hardwood that comes in two different styles. Plain wood veneer has wood grain on the top and a plain back. Heat activated veneer has a backing made of heat activated adhesive. Plain veneer is typically attached using either carpenter's glue or contact cement. When subjected to too much moisture, veneer has a tendency to bubble or lose its adhesive and come loose.
Dampen a rag and wring it out well. Lay it over the bubbled or blistered area. Heat a household iron to its highest setting. Set it on top of the rag and press down firmly. Leave the iron on the spot for 10 seconds.
Remove the rag and use a roller or rolling pin to press the veneer into place. Set a flat board on top of the repaired area and weigh it down with a brick or heavy books. Allow the weight to remain on the repair for 24 hours.
Create a small incision in a blister that does not respond to heat. Use a utility or craft razor knife to make the cut.
Inject a small amount of wood glue into the blister and press down to expel any extra glue. Wipe the excess with a damp rag.
Place a piece of waxed paper over the repair to prevent sticking, and clamp a piece of scrap lumber over the repair, or weigh it down as described in the previous steps.
Lift loose veneer at the edge and scrape any debris or old adhesive from the substrate and the veneer backing. Acetone or heat can be used to soften old adhesives. Do not use heat on areas dampened with acetone, though, to avoid the risk of fire.
Apply a thin coat of carpenter's wood glue to the substrate under the veneer. Spread it as evenly as possible. Allow the glue to set for several minutes before pressing the veneer into place.
Press the veneer into place and wipe any excess glue with a damp rag. Clamp a piece of scrap wood over the repaired are to hold it down, or weight it with bricks or books. Allow the board to remain in place for 24 hours.
Clean up any glue around the edges with a piece of fine-grit sand paper or a fine-grit sanding sponge. Sand with 150-grit or finer for the best results.