What determines the "vigor" of a fermentation?

Is it the OG of the wort, the fermentation temp, the constituent grains, the phase of the moon, price of tea in China, or what?

3 weeks ago I pitched a pack of re-hydrated Notty into 5.5 gallons of a 1.053 nut brown ale set to ferment at 65 and had krausen through the airlock. 3 days ago I pitched a pack of re-hydrated Notty into 5.5 gallons of a 1.040 blonde ale set to ferment at 68 and haven't had a blip in my airlock.

All those items listed and more (Well maybe not the price of tea) but there are factors too numerous to track regarding fermentation, some of which are completely out of our control, as you mentioned, moon phase, that does effect it.

Keep on brewing my friend

With the heavily-repeated caveat that airlock activity is not a useful indicator of fermentation...

There are a number of things that can affect your fermentation. Things that come to mind are conversion of starch into fermentable sugars during mashing, percent of dextrinous malt, mash/wort pH, temperature, aeration of the wort, temperature difference between yeast and wort at time of pitch... the list can go on for quite some time. Yeast can seem like fickle creatures but they most often get the job done, even if it looks like they aren't doing any work.

Specific gravity is the only way to truly tell if/how well a fermentation is going. If your blonde ale is still up in the 1.03x area, then you might have gotten a bad or old packet of yeast, though that seems unlikely with dry yeast. Either way, give it a couple more days (and test gravity each day) before you think about re-pitching.

Different yeast strains do perform differently but as long as pitch rate and yeast health were good then ime for a given yeast strain, temperature is the biggest factor influencing fermentation vigor. It's actually one of the things I use to determine fermentation temp; not too slow, not too fast.

As for how fast it takes off, that's completely different.

Read this, and don't worry what your airlock does or doesn't do....

https://www.homebrewtalk.com/f163/fermentation-stop-go-220828/#post2593681

I didn't mean to give the impression I'm concerned about my current batch as I'm not - I'm fully confident the yeasties know what they're doing. It just got me thinking about how different the 2 batches appeared even though the same strain of yeast was used on both.

jmf143 said:

I didn't mean to give the impression I'm concerned about my current batch as I'm not - I'm fully confident the yeasties know what they're doing. It just got me thinking about how different the 2 batches appeared even though the same strain of yeast was used on both.

Click to expand...

But that is precisely why external visual cues like airlock bubbling and even krausen development are not as good or accurate indicator of what is happening "under the hood"....and why the one consistant indicator is gravity reading.

All krausens look different, even using the same yeast on different batches.

The amount of krausen can vary for whatever reason, it can come quick and depart quickly or it can linger long after fermentation is complete, and it all be normal.

There is nothing "typical" in brewing...every fermentation is different, and should not be used to compare one with another...you can't do that.

No two fermentations are ever exactly the same.

When we are dealing with living creatures, there is a wild card factor in play..Just like with other animals, including humans...No two behave the same.

You can split a batch in half put them in 2 identical carboys, and pitch equal amounts of yeast from the same starter...and have them act completely differently...for some reason on a subatomic level...think about it...yeasties are small...1 degree difference in temp to us, could be a 50 degree difference to them...one fermenter can be a couple degrees warmer because it's closer to a vent all the way across the room and the yeasties take off...

Someone, Grinder I think posted a pic once of 2 carboys touching each other, and one one of the carboys the krausen had formed only on the side that touched the other carboy...probably reacting to the heat of the first fermentation....but it was like symbiotic or something...

With living micro-organisms there is always a wildcard factor in play...and yet the yeast rarely lets us down. So it is best just to rdwhahb and trust that they know to what they are doing. It sounds like you are brewing by a calendar, or instructions and not by what your beer is really doing, the problem is that yeast don't know how to read so they seldom follow their scripts. They dance to their own tune and its seldom 4 x 4 Time.

Don't assume the worst with the yeast, realize that they've been making beer since long before our great great great grandfather copped his first buzz from a 40 of mickey's out back of the highschool, so they are the experts.

Yeasts are like teenagers, swmbos, and humans in general, they have their own individual way of doing things.

And worrying because it's not happening how fast or slow you think it should be is really not worth the energy.

It may not be what you expected it to be but that doesn't mean anything's wrong.

I find that brewing is a lot more stress free if I don't compare one batch to another. I subscribe to the I trust the yeast club. They've never let me down. But I don't try to understand them...

But that's also why I say not to go by Krausen as a "sign of complete fermentation" either. The amount of krausen can vary for whatever reason, it can come quick and depart quickly or it can linger long after fermentation is complete, and it all be normal.

For example, I had a wit beer that I pitched bottle harvested Hoegaarden yeast on Dec. 26th, LAST YEAR that STILL had a 2" krausen on it three weeks later. I took a grav reading and it had reached terminal gravity, 1.010. So the beer was done, but the krausen still lingered. I finally gently swirled the beer to knock it down, and let it settle for another week before I bottled it. I'm not normally a fan of knocking them down, and usually let it do it naturally.

But some yeasts are low flocculating, and may have a difficult time. I figured since mine was bottle harvested, and I had pitched the starter at high krausen, maybe it was "genetically mutated" with the flocculation "gene" off or something. So I gently swirled it and let it fall.

I brewed another batch with another mason jars worth of that yeast several months later and had the same thing happen.

Beligan wits are notoriously long krausening.

That's why it's fruitless to try to use those things as indicators, they aren't consistent from one batch to another....even witht the same yeast.

I'd say the two biggest factors are temperature and the yeast strain itself. I use English ale yeast in most of my beers and regardless of the composition of the wort I feel like this strain acts pretty similar across batches. When I've noticed a difference, it's usually because I let the temp get away from me (I'm talking 2-4 degrees max). This sends it into overdrive.

If I could take the ester level, I bet I could ferment a 1.060 beer in 2 days with this yeast at 72 degrees.

I'm sure every other factor in brewing also has an effect on fermentation vigor but I suspect the changes are so difficult to detect that it would be hard to quantify.

jmf143 said:

I didn't mean to give the impression I'm concerned about my current batch as I'm not - I'm fully confident the yeasties know what they're doing. It just got me thinking about how different the 2 batches appeared even though the same strain of yeast was used on both.

Click to expand...

It could be a number of things or it could just be that one packet was really healthy and the other one wasn't. Also, one beer was a dark beer with higher gravity than the other which was a light colored beer. If you brewed both with the same water the dark beer should have a lower pH than the low-gravity light-colored beer. One of the first things the yeast do is pump protons into the wort to render a much lower pH outside the cell wall than inside it. They need that pH differential in order to bring sugar inside the cell to be metabolised. Or maybe one packet was really healthy and the other one wasn't.