Well we made it through the night with no explosions, but the krausen did overflow at some point while I was sleeping so I suspect that with a fully sealed lid it would have erupted again. This points to the krausen stopping up the airlock ( tried both a double bubbler and a single piece unit and a blow off tube ) which causes the explosion ( just like you said pommy ). I have a free carboy so I was thinking of lightly stirring the mixture to get everything mixed well and then transferring half of it to a carboy to finish fermenting. Anyone have any experience with that? Could I possibly interrupt the yeast somehow by mixing them up 2 days after pitching?
Also, does OG have anything to do with the overactive fermentation? This is the highest OG that we have attempted so far ( still not extremely high, 1.08 I think ) and by far the most active fermentation. Or is it just luck of the draw and we happened to pick up an overachieving tube of yeast?