Wednesday, November 14, 2012

Hand Shaped Corks

You've probably heard the term "hand shaped corks," but what does that mean?  Are these corks on your flute really shaped by hand?  Well, the answer is yes!  We recently caught up with flute finisher Karl Kornfeld to take a look at the process.

Corks are used on the trill keys, G# key, and D# key.  Powell receives a supply of corks in the shape of small "barrel-type" pieces -- similar to a cork from a wine bottle.  One cork piece will be used for the 4 keys mentioned above.  The cork is first cut into quarters.  Karl prefers to take one of the quarters and then cut that quarter in half for the trill keys.  This helps with consistency and allows for these corks to (aesthetically) "match."  When we caught up with Karl, he was working on a D# cork.  For this key, he uses one of the cork "quarters."  He uses contact cement on one side of the cork and the back of the key.  Then, he presses the two together and holds them (with the help of some equipment) until the glue is dry (about 10 seconds).

Now the shaping process begins.  The cork must be shaped so that the key opens to a standard measurement that Powell uses on their flutes.  A cup height gauge is used to periodically check the height of the key cup opening as the cork is shaped.  Finishers use a combination of double-sided razor blades and various grits of sandpaper (220, 400, 800).  The higher the grit, the finer the sandpaper.  Karl puts the key mechanism back on the flute and marks the cork in the center, where the cork touches the center of the "box" (box is the area between the sides of the ring).  He then begins to shape the cork with the combination of sandpaper and razor blades.  In the photos below, the thin strip of sandpaper is 220 grit, and the larger piece is 400.  The 800 grit is used for very fine adjustments.  He continues sanding and shaping the cork until it is the correct size and shape for the key to open properly at the calculated height -- which is critical. 

There are other mechanisms which have cork for adjustments, and for these, small slices of the original cork are used.  So, now if you hear the term "hand shaped corks" with Powell flutes, you'll know that they are truly hand shaped by our finishers!

It begins with a piece of cork.
Cork piece divided into quarters.
One quarter piece for the D# key.
Applying contact cement to cork (and then key).
Pressing key and cork together.
Holding key and cork together until glue dries.  Leather strip is used to protect key.
Shaping cork with razor.
Marking center of cork where it meets center of the "box."
Sides of cork should not touch sides of ring.
Some shaping with a 220 grit strip of sandpaper.
Checking key opening with cup height gauge.
More shaping with a 400 grit piece of sandpaper.
Quarter cut in half to match trill key corks.
Slice of this piece used for adjustment cork.

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