 Driving rain, water gets down in there and it continues and continues and continues. Efflorescence starts on the outside of the chimney. So it's telling you there's a problem. The other thing is, again, just as I described, a crack in the crown wash, water's getting down. So can the brick from the backside and eventually that efflorescence blooms on the outside of the chimney. It could be that the brick itself is just absorbing a lot of water.