Occasionally on an older piano that has been subject to dry conditions, it is not uncommon for the glue joint where the hammer meets the hammer shank to become loose. This is usually indicated by a noticeable clicking sound when that note is played. Heating the joint facilitates the removal of the hammer for piano hammer regluing.
Piano Hammer Regluing
BEFORE: This image shows before piano hammer regluing.
The old glue is removed by sanding, because new glue does not stick to old glue. New glue is applied.
AFTER: Here is an example of hammer regluing on an older Young Chang grand piano I serviced in Rockland County NY. The black coloring is a result of the heating process and is wiped clean upon completion of the repair.