Fermentation bubbles speed up

I try to regulate the temperature in the bathroom where my secondary fermenter resides. It's on day 7 (day 2 in secondary), and when the ambient temp begins to approach 70, I spray the towel that I've wrapped around the glass carboy with water. Never fails, this starts making the bubbles push out about every 5 seconds! Anyone know why this happens? Is it really affecting the beer temperature that quickly? Is it the gentle pressure of the shower head on the glass/towel that would cause it? Reason for concern?

Are you sure it's not sucking water back into the fermenter? In theory, cooling the wort/fermenter should reduce the amount of pressure in the vessel.

JMSetzler said:

Are you sure it's not sucking water back into the fermenter? In theory, cooling the wort/fermenter should reduce the amount of pressure in the vessel.

Click to expand...

I make sure to avoid spraying anywhere near the top. Only thing I can think of is that the glass is cooling/contracting very slightly, affecting the pressure..

The glass is not contracting enough to make any difference. Glass is very brittle. If it contracted (or expanded) enough to make a pressure difference, it would break. The beer inside the fermenter will expand and contract slightly with temperature changes, but the real expansion and contraction that takes place with temp changes is the air in the headspace of the fermenter. Cooling that air a couple of degrees would potentially suck water out of the air lock back into the fermenter, but it would not create an expansion of that air to create pressure bubbles through it.