Touchweight -- Downweight in particular

Touchweight refers to the force associated with the response of a key on a piano.  Downweight specifically refers to the amount of force necessary to depress the key; upweight refers to how much force would stop a key from returning to its original position.

I've been finding that I've been getting tired at the piano faster than I remember.  My left wrist is actually hurting a little bit.  Maybe it's because I'm practicing more, but I have an alternate theory.  New York City had an extremely humid summer, and my technician told me that it caused many pianos to have "stuck keys", and I wonder if it's had a permanent effect on my piano.

Most grand pianos apparently have downweights in the 50 gram range.  Back then, I asked my technician to make the action slightly heavier, but he never told me what downweight he was aiming for.  Apparently most piano makers these days aim for 52-55 gram downweight.  Here's a link on the pianoworld forums with useful information:

http://www.pianoworld.com/forum/ubbthreads.php/topics/105454/1.html

Using quarters and dimes, I weighed the downweight for all the keys on my piano, the the pedal down.  A quarter weighs 5.67 grams, a dime 2.27 grams.  After testing a few keys, the weight of 10 quarters appears to the the average downweight, so I just taped 10 quarters together to save time.  Let's just say that's 56.7 grams.

A total of 58 keys, or 65.9%, of the 88 have downweight less than 56.7 grams.  Presumably, around 55 grams was the factory setting.  The distribution these 58 keys is interesting: from the very top octave to the bottom, it goes 13-10-8-9-6-3-6-3.  13 because it goes from C-C, the last 3 is low A, low B flat, low B.  Maybe I'm generalizing a little, but the more often used keys are more messed up.  There's also the "noise" in the data since my technician oiled up the bushing for a few of the notes somewhere in the middle to upper register.  Either way, I'm guessing they're messed up more because I was playing them when the bushing absorbed lots of moisture.

A few downweights are way, way off.  The lowest D weighs a whopping 76 grams!  The second lowest E is a close second, weighing 73.7 grams.  8 of them weigh over 68 grams, all of them in the 2 lowest octaves (starting from low C).  Perhaps that explains why it's especially my left hand that's getting tired?

I haven't measured upweights.  I've already wasted enough time testing the downweights.  But the second lowest E actually doesn't even always return to original position, so... that's definitely problematic.  I've had to work super hard for repeating notes for some keys, so it'll be interesting to find out what keys should give me problems.

Looks like I'll need to do something about it at some point... maybe the next time I get my piano tuned.