Agreed that the extended meaning of "rim weeping" is classic
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Applying the match to the tobacco with, from what I understand, release of moisture is specifying at what point combustion/condensation occurs. Maybe?
I smoke Escudo in the REO and Cumberland in the AeroBilliard. I'm at the beginning of smoking a second tin of Escudo in this pipe. I've had this pipe since December and probably smoked it a dozen times. Good smoker. I've only had the AB since May and smoked it about the same number of times. Also a good smoker. I've smoked many tins of Escudo and Cumberland before in other pipes without incident. Whether the tobacco/pipe relationship has anything to do with rim weeping is anybody's guess.
As regards the substance I'd say it's water; I checking the REO for stain but it was clear.