Thursday, January 10, 2013

Getting a Grip on Key Pads

A Powell flute has Straubinger pads, which for most keys are held in place by screws or bushings.  But, alas, there are some pads on a Powell that are held in place by shellac.  We visited the repair shop when Rachel Baker was just about to seat or "float" some pads into place.  Specifically, the C1 and trill keys on a Powell are held in the key cups by shellac.  It seems like it would be pretty straightforward, but we realized there was much more to it than we thought.  Rachel told us that the shellac needs something to grab onto, so the inside of the key cup and back of the pad need to be "scored."  Scoring is a process that makes the surfaces a bit more "rough" so the shallac can grip these surfaces. If the pad and key cup are not scored, the pad could fall out easily over time.

To score the pads, Rachel takes a tool with a sharp, needle-type tip and pokes holes in the back of the pad.  She does this whenever she replaces the pads held by shellac (C1 and trill as mentioned above).  The pads on these particular keys are replaced on a C.O.A. if necessary and always replaced during an overhaul.  She also checks to see if the inside of the key cup has been scored.  If not, she takes a scraper and scores the inside of the cup by making a few lines in the metal.  The shellac is then heated, and the pad is "floated" into place.  With the back of the pad and inside of the cup scored, the shellac now has something to grab onto, and the pad should stay securely in place!

About to score back of pad with the needle-tip tool.
Poking very small holes to score back of pad.
Scraper is used to score the inside of the key cup.
Making lines in the cup to score it.
Scored key cup and pad.
Heating shellac with an alcohol lamp.  Heated shellac will then be applied to pad to "float" it into place in the key cup.

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