When you need to separate a joint that has been sealed with wood or polyvinyl acetate glue, it is sometimes possible to soften the glue. Doing this allows you to separate the two pieces of wood without causing damage to either of them. Polyurethane glue, however, is waterproof and therefore harder to soften and separate.
Moisten the glue with water
If possible, wrap the wooden joint up in a wet towel for 24 to 48 hours. Do not let it dry out during that time, so keep moistening it. As the water seeps into the glue, the glue will become soft. It is then possible to wiggle the joint apart.
Soften the glue with white vinegar
If water does not work to soften the wood glue, or if you are unable to wrap a towel all the way around the joint, drill small holes into the joint that are no bigger than 1/8 inch in size. With the holes arranged to be vertical, squirt white vinegar into them. Let it soak until the glue softens. If you are dealing with polyurethane glue, fill the holes with lacquer thinner or acetone. Keep refilling the holes every hour until the glue has softened enough to pull the wood apart.
Heat the glue
Use a heat gun or a blow dryer and try to soften the wood glue by heating it. If you already tried to soften the glue using lacquer thinner or acetone, do not try this step, as both chemicals are flammable.