Cold Crashing

[Beerbuddha]

Just looking for other people's procedures on the contraction of the beer when crash cooling ! Or air space above which causes a vacuum and as I have learned will suck the liquid from blow off tube into the beer. I only discovered this issue due to having clear fermentation vessel.

As I used star San it was no issue really I just siphoned from under star San layer.
To eliminate this I use normal small airlock after primary fermentation completed.
But issue is .......when the beer is cooling it will still suck in air from outside which Might cause an issue so I was woundering what others do in this case ?

[Parky]

By the time the beer is due to cold crash I've usually replaced the blow off tube with a small bubbler (see below). I've found a blow off tube is not necessary on my set up once the initial fermentation has settled down, so I replace it with an airlock.

I'm currently brewing a lot of small batches in 5L plastic 'bottlejohns' with airlock on top. I find the issue you describe comes up a lot for me, not just when cold crashing, but anytime I move the bottle. The plastic tends to flex when I lift the 5L bottle and air is sucked in through the airlock.

My workaround for this is to keep the amount of liquid in the airlock to a minimum, i.e. just enough to cover the 'U bend', but not enough for the liquid to make the leap over the top and into the FV (see pic below).

[Ned]

As I was telling you earlier B.B., I cold crashed & managed to suck approx 300mls into carboy. I siphoned from the middle & kegged. Had a quick taste and wasn't convinced it was o.k. I'm hoping it is not infected as the tube ended up being opened to air once it sucked up all the starsan. Live & learn. I'll let you know in a few weeks if it's alright. Not sure if it's my imagination but beer looked nice and clean in fermenter but real cloudy after starsan addition? 😕

[Beerbuddha]

Yep that's the way to go. I think most make the mistake of leaving blow off in place.
But the next issue is when a vacuum is made in the fermenter it has to suck something in and now the bubbler is in place it has to be the unfiltered air in you fermentation fridge or storage area which is what u are trying to keep out of the fermenter.

[Beerbuddha]

It has happened to me also hence the post to get other people's taughts.
My beer was fine when I siphoned from below star San layer.

[Parky]

But the next issue is when a vacuum is made in the fermenter it has to suck something in and now the bubbler is in place it has to be the unfiltered air in you fermentation fridge or storage area which is what u are trying to keep out of the fermenter.

Too true!

For me, I'm only leaving the beer to cold crash for a day or two. I figure the amount of air that may be drawn in isn't enough to affect the batch. Besides, CO2 is heavier than O2, so in my imagination the CO2 produced during fermentation will act as a buffer for any incoming air.

Air will have to enter the system at some stage, even when bottling, so it's unavoidable unless you create a sealed system (or have access to a CO2 tank. I think the amounts involved aren't really going to be a huge issue though.

However, if you did want to create a sealed system - pop a balloon, or even a loose wrap of cling film, over the top of the bubbler airlock with an elastic band a day or two before cold crashing. That way the balloon will have filled with some CO2 from the FV, and it will just be this CO2 that will be sucked in when the inevitable happens 

Of course, if you don't want to go for the DIY solution check out this bad boy -

http://www.amazon.com/Midwest-Homebrewing-and-Winemaking-Supplies/dp/B0064ODQQG

[Beerbuddha]

Ah not another piece kit I want but don't need 

As you say it's probably not gonna cause an issue. It hasn't for me so far but interesting to see if others realize it can happen !

If I didn't have a clear fermenter I doubt I'd have noticed the issue with blow off tube and then left scratching my head as to why my beer is bad.

[TheSumOfAllBeers]

The headspace contracts much more significantly than the liquid, and is the real problem.

[Beerbuddha]

Hence the" Or head space above " .
Just don't get into pressure ...volumes..temp index graphs 

[Beerbuddha]

This is what issue looks like in fermenter.

[Parky]

Put on a brew over the weekend using a new bucket FV, but didn't have time to install an airlock, so just left the top of the bucket slightly open.

Was a bit hesitant about not having an airlock in place and did a bit of research to see if it would be bad news for the fermentation. One line from another forum challenged my thinking about why I'm using an airlock in the first place -

An airlock is simply a vent, a VALVE to release the buildup of excess co2, to keep your beer off the ceiling. Whatever means used to achieve that end is fine. The yeast don't care.

I hadn't thought about an airlock that way before - so as long as airborne particles are kept out of the brew and there's a means of escape for the buildup of CO2 during primary fermentation, everything should go according to plan. Will see how the current brew goes over the next few days.

Thought this video was of interest too -

https://www.youtube.com/watch?v=X9xT8DHOZFE

Anyway - back on topic -

I also read online of brewers using a dry blow off vessel (e.g. empty jug), instead of putting the blow off tube under starsan/water. The logic here seems to fit with the quote above - that a blow off tube is simply that - a means to vent a buildup of gas/krausen.

If nothing else it's another way to prevent bad things happening to the brew as a result of back pressure in the FV 

[Qs]

If you are worried about this happening you can use vodka instead of Star San.

[beerfly]

was just reading this about lagers earlier and they had a nice workaround for the pressure drop

Note that during this temperature change, it is likely that the liquid from a 3 piece airlock will be "sucked back" into your fermenter due to the pressure change in the vessel. Considering removing the airlock and placing a balloon over the bung to prevent oxygen from being drawn in.

[Beerbuddha]

Great replies guys lots food for taught.
Looks like I need a conical fermenter added to wish list.

[neoanto]

Guys what temperature is normal to cold crash at?
I have a Hobgoblin ale chugging away and i will cold crash for a day or two before bottling.
I dont know what temperature i should do this at though, any advice would be appreciated!