Old lead/swelling in keys (LONG)

[Avery Todd]

Rolland,

   Below is a compilation of posts I've saved from a discussion on this
subject in June 1996. Hope some of it is useful.

Avery

>I am working on an old grand action about 1926 in which the key leads have
>swollen to the point that they interfere with the adjacent keys.  I can file
>them down or replace them.  Any suggestions welcome.
>Thanks again, Rolland Miller, RPT <rmiller@en.com>

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Don't inhale that SH--T or you might find yourself stuttering more often.
Lead oxide is POISON!   Don't inhale or ingest it!  It won't go through your
skin.

David C. Stanwood

============================================================================
>>    What causes the lead in keys to corrode?  Why do some key leads corrode
>>    and others do not?  What, chemically/physically, is REALLY happening
>>    here?

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>Salt air, if you live in CA, FL or HI.  Seal off the lead (e.g., with
>shellac)
>from the air and the reaction is slowed dramatically.  I have found key leads
>so swollen that I had to break keys in order to get them out of the piano.
>
>Kirk

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<What causes the lead in keys to corrode? >
< a by-product of the lead alloy allows the corrosion to occur?>

I am new to the list, but let me jump in here because I have worked with
lead, and alloys of lead in several different disciplines.

Pure lead is very inert, -dump it in water and 10 years later  it is
essentially the same, only the slightest sulfide coating- generally. Hey, -
that is why they used it in plumbing since the days of the Roman empire.

Alloy the lead with other metals, like antimony, tin, bismuth, etc. - and you
have a solid battery (dissimilar metals with different potentials)  that will
erode itself to swiss cheese  in a few weeks in water. Humidity will also
affect this alloy by eventually causing a white lead oxide.

A Test ------ pure lead is very soft, even a dull knife can cut off a shiny
chip easily.   If the lead is alloyed, the hardness increases considerably, a
knife will chip off a crumbly piece, and the surface will be  gray, not
mirror shiny.

<Why do some key leads corrode and others do not? >

I suspect that action makers used about the cheapest lead weights they could
get, which were probably old contaminated linotype slugs from printing
plants. ( 5% tin, 13% antimony, rest lead, with copper as a contaminant.-
they alloyed for hardness to make type print longer.)

 <Is there a chemical reaction occurring between the lead and the "treated"
wood in some key  sticks?>

I doubt it, unless the keys were wet.

 <Is it an oxidation process that is occurring as a result of a particular
atmospheric environment?>

Possibly a little, but not with pure lead weights.

<What is the best and safest approach/method to correct non-functioning  keys
because the lead is so "puffy?" >

Shave the excess off with a sharp chisel, -being careful not to eat the
shavings.

<Could one "seal" key lead to inhibit the oxidation process?>

Sure, a swipe of paint ot varnish should do it. I used to sandblast the
oxidized key leads (because I had a sandblaster setup) - and then put a spot
of varnish on them. You can just varnish the oxidized leads with a thin
mixture that penetrates the oxidation and then hardens up,- trapping the evil
oxides in place.

Random thoughts,
Bill Simon

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As for keys with lead so swollen that one has to break keys ...
I too have had keys that were so seized by swollen leads that they would
not move at all.  Indeed they were being forced outward by the pressure
generated.  However, I have not had to break any keys.  I have always
been able to insert a hacksaw blade between the keys and to cut through
the leads.  Often going every other key will be enough to allow them to
be forced off the keyframe.  Once off the keyframe, it is relatively easy
to cut the leads back flush to the key with a sharp chisel.

Ed Hilbert

___________________________
Avery Todd, RPT
Moores School of Music
University of Houston
Houston, TX 77204-4893
713-743-3226
atodd@uh.edu
http://www.music.uh.edu/

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