Traditionally, doors have been made from solid wood. Modern doors are frequently made of manufactured wood products such as Medium Density Fiberboard and hardboard. In order to create the look of solid wood, these doors are often covered with veneer. Veneer is a thin layer of hardwood that is affixed to the base material with an adhesive. Variations in humidity and temperature are the primary cause of damage to veneer. Most repairs are simple.
Remove the door from its hinges and lay it flat on sawhorses or another flat sturdy surface. Examine the veneer to determine what type of damage you have to repair. The most common types of damage are loose edges, blisters in the centre of the veneer, and splits in the veneer.
Glue damaged edges down with wood glue. Lift the loose edge carefully and remove any debris and old hardened glue by scraping with a razor scraper. Blow the dust from under the veneer to insure a clean bond. Spread a thin layer of wood glue under the veneer and press the veneer into place. Wipe excess glue from the edge with a damp rag.
Place a block of scrap lumber on top of the repair area and clamp it down with a c clamp. Leave the clamp in place for 2 to 3 hours before placing the door back on its hinges.
Slice blisters open carefully with a utility knife. Inject a small amount of wood glue into the opened blister with a syringe. Press the veneer in the blistered area down with a rolling pin to flatten the veneer out. Cover the blister with a piece of wax paper.
Place a block of scrap lumber on top of the repair. Clamp the lumber down as for loose edges or weight the wood block with bricks or heavy books and leave the weight in place for 2 to 3 hours to allow the glue to harden.
Inject a small amount of glue into open splits. Cover the split with wax paper and clamp or weight a scrap wood block on top of the repair area. Allow the glue to harden for 2 to 3 hours. Remove the clamp or weight and woodblock and wax paper.
Fill any remaining gap between the pressed sides of the split in the veneer with a solvent-based wood filler of an appropriate colour. Sand the filler to smooth the surface. Apply a coat of matching stain with an artist brush to the filled area. Apply a coat of clear nail polish over the repair to complete it.