Permatex automotive gasket sealer comes in several hardnesses.  One grade
stays like leather, another gets fairly hard, and so forth.  The binder
is shellac, with some kind of filler and non-volatile oil (castor oil?) to
keep it from becoming rock-hard.  I have created my own burnt shellac for
sealing situations where no flexibility is needed, but the Permatex is
great for the kind of situation you described with the lead tubing.
Cleanup is done with methyl alcohol.

Four feet of snow, with drifts up to eight feet, has fallen on Victoria
over the last three days, the worst storm since 1916.  The city is
paralyzed.  I shoveled three feet of snow off my laundry room roof.  The
roof is low pitch, with widely spaced old rafters, and vulnerable to
collapse, particularly when the snowfall turns to rain.  Then the snow on
the roof becomes a huge sponge and gets _really_ heavy.  Not exactly what
the doctor would recommend me doing two weeks after gall-bladder surgery!

Cheers,  Doug

 [ When it gets head-high, Doug, "Keep your chin up!"  -- Robbie