A.Both yellow and white PVAs will soften and lose some of their grip if you saturate the joint with hot vinegar. Use a syringe to introduce the hot vinegar. If necessary, drill 3/32-inch holes in an inconspicuous spot to get the hot vinegar into the joint. Let it sit for at least 30 minutes, and rewet the joint if it looks dry. Then try to wiggle the joint apart. Do not whack it with a hammer (at least, not very hard), as you run the risk of breaking the wood.

— J.J.

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