Fermentation slowed, then sped up again

[Bacon488]

I'm making NB's Black IPA kit with Pacman. I pitched a 1 liter starter into 5 gallons of roughly 1.080 wort with Wyeast nutrient and plenty of O2 from a stone, and very vigorous fermentation took off within hours. It went like gangbusters, then slowed down after a few days, at which point I replaced the blow off tube with an airlock. Now, in the few days since, I have seen the rate of airlock bubbling slow down from 9-10x/min to 4x/min before starting to slowly increase again to over 7x/min, in a 3 day period. The temperature of the room has been kept pretty constant, with just a couple degrees increase in the last couple of days, so I don't think that's a significant factor.

My first thought when I see something out of the ordinary with the fermentation is "infection." Should I be worried that my fermentation began speeding up again, even a little bit?

 

[Revvy]

Your reallty don't know if your fermentation slowed down and spend up, just that your airlock did...that really isn't the same thing.

Airlock bubbling and fermentation are not the same thing. You have to separate that from your mindset. Airlock bubbling can be a sign of fermentation, but not a good one, because the airlock will often blip or not blip for various other reasons...so it is a tenuous connection at best.

If your airlock was bubbling and stopped---It doesn't mean fermentation has stopped.

If you airlock isn't bubbling, it doesn't mean your fermentation hasn't started....

If your airlock starts bubbling, it really doesn't matter.

If your airlock NEVER bubbles, it doesn't mean anything is wrong or right.

Your airlock is not a fermentation gauge, it is a VALVE to release excess co2. If it bubbles it is because it needs to, if it doesn't, it just means it doesn't need too...

Often an airlock will bubble if the fermenter has been disturbed in some way, like a change in temperature, change in atmospheric pressure, the cat brushing against it, opening it up to take a hydro reading, any number of things. The co2 has sat in stasis for a period of time, then it was disturbed so it is not longer at equilibrium with everything else now. And therefore it is blipping in your airlock...

Or you could indeed have fermentation happening, since maybe your fermentation was laggy and a change in temp restarted fermentation.

Airlock bubbling only tells you that co2 is coming out of the airlock, it is not telling you why. And there's various reasons. That's why it's not a good idea to equate airlock bubbling with fermentation...It could be because it is fermenting, or it could not be because of fermentation...so it's not a trustworthy tool.

Either way I wouldn't worry about it.

 

[Bacon488]

Come to think of it, the barometric pressure did rise for a couple of days and then drop for a couple of days, and it's still dropping now...

Thanks for your reply. Intellectually I know that the airlock isn't a fermentation gauge, but it's hard to see it speed up and not think, "It's creating more CO2 than before." No, it's just releasing more. I've got seven stitches invested in this batch (dropped a carboy) so I'm probably a little more sensitive than I might be otherwise. Gonna go RDWHAHB now.

 

[Revvy]

Come to think of it, the barometric pressure did rise for a couple of days and then drop for a couple of days, and it's still dropping now...

Thanks for your reply. Intellectually I know that the airlock isn't a fermentation gauge, but it's hard to see it speed up and not think, "It's creating more CO2 than before." No, it's just releasing more. I've got seven stitches invested in this batch (dropped a carboy) so I'm probably a little more sensitive than I might be otherwise. Gonna go RDWHAHB now.

You just hit the nail on the head.....That is exactly what brewers need to realize....We can't tell just by looking if co2 is being generated, or being released...Or being released some place other than our arilock, like the grommet.