I am in the final phase of my Knabe grand restoration.  I ran into
the same problem with the lead elbows.  I was unlucky enough to be
under the elbows when I found out what was inside...

I was under the piano taking the original tubing apart when I was
doused with a large amount of grayish-black powder.  Fortunately,
I had my glasses on, otherwise it would have dumped right into my
eyes.  As it was, it looked as if I had done a minstrel show.

The books don't warn you of this and this is my first ground up
restoration.  I'm sure I inhaled enough not to be good.

Merry Christmas to you all,
Donald Cochrane