Fermentation Lag Time

Lag time is how long it takes your ferment to start, after all is brewed and the yeast is pitched into the wort.

Ideally in a perfect world, your ferment takes off in a few hours. I have seen a ferment begin in as little as 4 hours after pitching yeast.

But it ain’t a perfect world, is it?

The longer it takes, the easier it is for unwanted bacteria nasties to begin their own colonization of your wort…that would be bad.

If you are still looking at your airlock for activity after 24 hours, you may consider a backup yeast plan…you do have a backup dry yeast, just in case, don’t you?

Certainly, given the hundreds of varieties of the liquid yeasts out there, we can create some very specific beers to suit our palate. On the other hand, a packet of dry yeast can save your beer from ruin if something went wrong with your sanitation procedures, an old batch of yeast, or some extreme temperature differences between your wort and pitched yeast…it is recommended that your wort and yeast be within 10 degrees of each other when pitching…any more than that will increase your lag time.

This is why we make a starter; to assure we get a gazillion or so yeast cells into our wort to kickstart the ferment as soon as possible.

You may remember that we cooled our wort down to 100°, then poured it into our carboy. I also added a gallon jug of chilled water to the carboy before adding the wort to the carboy, to further cool the wort. The ambient temp here is about 75°.

If the wort is say 85°, and our yeast starter is 75°, and we pitch it at that point, that will increase our lag time. The wort will cool itself to the ambient temp, and that could take hours. One can watch the airlock, and it will reverse; in other words, as the wort cools to ambient temp, it will contract and suck air back through the airlock until the wort temp matches the ambient temp…it could take hours. The airlock may have to be removed and replaced again and again as the temp equalizes, so as not to suck in whatever liquid you have in the airlock…I use bourbon or rum in airlock.

Given that our yeast in this batch is old, we have already seen that old yeast takes longer to get started.

This is about 6 hours after pitching the yeast. Not bad…a nice kroysen forming on top. The airlock is bubbling, and will put on blow off tube overnight…just in case.

And this is a video I prepared an uploaded this morning

It’s doubtful it will blow the top off, but watching the beer swirl and churn as the yeasts multiply over and over again and again until all the sugar (malt) is gone, or they run out of O2 (not bloody likely).

If all goes well, the yeast will consume all the sugars, and the gravity will drop to the expected 1/4 of OG, then we move to the next step.

You may have noticed a black t-shirt wadded up on top of the carboy. I keep the carboy covered, as exposure to sunlight can affect the hop oils, and make them skunky. Although it only gets direct sunlight in the late afternoon, the light fixture above is a 6500K LED, and the spectrum maybe close enough to natural sunlight to do just this…so why take a chance?

I received my replacement yeast this morning. Its expiration is December this year, so slightly..slightly newer than the other two. We will use that to bottle in a couple weeks…stay tuned for progress.

2 thoughts on “Fermentation Lag Time

  1. Well, how long did it take to kick off?
    I have had summer ales brew out in a week in the summer that turned out to be excellent beers.

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