How to Remove Bubbles From Polyurethane Finish

Sand down the layer of polyurethane finish until the bubbles disappear. Make sure to apply minimal pressure to the sandpaper so as not to strip off any more of the finish than necessary. If the stripping goes too deep, it could lead to an uneven surface on the piece of furniture when the finish is reapplied.

Brush the sanded surface off with a soft rag to remove any grit or dirt. These particles could get caught in the reapplied finish, ruining the appearance.

Fill a deep cup halfway with warm water. Set the brush into the cup. Bubbles will emerge from beneath the brush's bristles; wait for the bubbling to cease and remove the brush from the water. Wring the brush out gently, so that the bristles are still moist but not soaked.

Apply a coat of the polyurethane finish to the sanded area with light, slow strokes. Do not over-brush the area, as that can lead to more bubbles or brush marks.

Wait for the spot to dry thoroughly and then check it for bubbles. Sometimes bubbles that show up in wet finish shrink or vanish as it dries. If there are still bubbles in the dry finish, repeat this process or strip the whole piece and finish it again.