I'm hoping those of you with expertise in this area might help me out.
I have a rank of Aeolian's free-reed clarinet pipes, and on a few of the
pipes previous tuners have had to push the resonators so far down past
the solder blob that the resonators have split along the solder seam.
For some reason those few reeds became flat enough in pitch that this
was necessary to get them to speak at the correct pitch.

At first I thought these few reeds might be dirty, since the reed
tongue is exposed to whatever might drop down into the pipe.  All I
found upon inspecting them was a reddish-brown substance that appears
to have been painted on the side of the tongue exposed to the
atmosphere.  All the reeds have this substance painted on them.

So I have a couple questions.  What is this reddish-brown stuff and
what purpose does it serve?  Does it protect the reed from corrosion or
is it a voicing aid?  And lastly, is there anything that can be done to
raise the pitch of the flat reeds so that the resonators can be
returned to their proper position

Thanks for any help you can give me!

Bruce Newman