Yeast/Fermentation Question.

[Chimera16]

New member here, my first question comes with a bit of an anecdote.

So I started homebrewing about 2 months ago. My last brew was a Irish Red which came out pretty good so I decided to kick it up a notch and try a Scotch Wee Heavy. Owner of the local brew shop helped with the recipe. 10 lbs of malt, bramling(?) hops, 1 lb of dark crystal, 16oz molasses, and pitched Safbrew S-33 Yeast. Within only a few hours, I had a quickly growing krausen. The fermentation was almost explosive within 24 hours, I had to put in a blowoff hose in because it was literally blowing the water out of the airlock. About 48-60 hours after pitching the yeast it seems as though my brew has stalled. The krausen is completely gone, and there is barely a bubble coming through per minute. Im using a gum stopper on a glass carboy with a nice tight airlock in. The temp on the fermometer reads somewhere between 66-70F, and I assumed this was fine for the yeast. I noticed while moving the carboy that any slight swirl seemed to get the yeast moving, and I got a lot of bubbles out.

Now, if I understand the fluid dynamics properly, the denser fluid (the still sugar-rich wort) is sitting on top of the less dense fluid (the newly created alcohol). The yeast, which I believe ferments up to 11.5% abv, is getting drowned out by a higher alcohol content. The swirl mixed the alcohol and allowed the yeast to get back to work.

Am I correct in this assumption and need/can do anything about it or am I just complete wrong in this assumption and need to relax and have a homebrew?

ps: Aside from the above dilemma, how should I split the time in secondary/bottles? Scotch Wee Heavy takes 3-4 months to finish, how should I divide the time?

 

[mosquitocontrol]

sorry about the engineer talk.

1. Dynamics = moving (i.e. flowing.) a fermentor should be relatively static
2. Denser materials will be lower then less dense.

 

[Chimera16]

sorry about the engineer talk.
2. Denser materials will be lower then less dense.

If you don't mind me asking, why does oil sit atop water? Aren't hydrocarbons heavier than water?

 

[Nurmey]

You got bubble going when you moved it because you knocked the CO2 out of suspension.

Yes, relax and have a home brew!

Four weeks in primary, eight weeks in secondary will bulk condition your beer very nicely.

Welcome to HBT!

 

[ajf]

Oil is less dense than water (which is why it floats on top). google relative density of oil if you don't believe me.
However, oil floats on top of water because it has a higher surface tension which prevents it mixing with the water. In the case of alcohol, it does not have a high surface tension, and it mixes with the beer aided by convection caused by the heat of fermentation.
The reason you get bubbles after moving the carboy is that there is a lot of CO2 dissolved in the beer, and moving it causes some of the CO2 to be released.
48 - 60 hours is a little bit fast for fermentation to complete, but plenty of brews do complete in that time. The only sensible way to verify if you have a stalled fermentation is to take a gravity reading. If it has reached the FG, it's done fermenting. If not, wait a few days and take another gravity reading. Although you may not see bubbles in the airlock, my bet is that the gravity will still be dropping, but slowly. This is perfectly normal. You just have to be patient.
I'd wait until the beer reaches the FG (which may take a few weeks), then either rack to a secondary for a couple more weeks, or leave it in the primary for another week to give the yeast time to clean up. You can then bottle and allow it to condition and mature.

-a.

 

[steelerguy]

The alcohol content is the same throughout the beer in the fermenter. You don't shake you beer bottles up before pouring do you?

Most of my fermentations go hot and heavy for 72 hours or so and then slow down quite a bit. Doesn't really sounds like yours is doing anything weird.

1. Dynamics = moving (i.e. flowing.) a fermentor should be relatively static

Maybe once fermentation is complete, but during the first few days of fermentation the liquid in the fermenter is anything but static!

 

[drayman86]

Oil is less dense than water (which is why it floats on top). google relative density of oil if you don't believe me.
However, oil floats on top of water because it has a higher surface tension which prevents it mixing with the water. In the case of alcohol, it does not have a high surface tension, and it mixes with the beer aided by convection caused by the heat of fermentation.

Not entirely correct.

Oil does not mix with water due to polarity. Water is slightly polar, therefore it will not dissolve solutions like oil that are non-polar.

In the case of ethanol, which is polar; this compound will mix freely with water, so the distribution of alcohol in a fermenter is even throughout.