Open fermentation / Foil Airlock

I read about open fermentation using aluminum foil. I understood that while fermentation bacterial contamination is almost impossible for two reasons, one: CO2 going out and two: the yeast activity. But when the fermentation slows down CO2 and the yeast activity drops the possibility of contamination raises.
My question is for the people who use open fermentation. When do I know the moment I have to close my fermenter to prevent contamination, without causing an explosion?

Thanks!

It is really interesting! My problem is only to know when transfer the wort to a closed container. Because I do not have a refretometer to measure gravity.
Is there any tip?

Thanks!

My fermenter is basically a bucket with a lid that is not airtight ( the Cooper's new style fermenter ).. It keeps the CO2 layer in place yet allows gas to escape freely.
The only problem with it might be if your krausen rises up too high and leaks out around the lid. This has never happened with my ales since there is a ton of headspace even with 6 gallon batches. I use Nottingham yeast and with proper temperature control ( 60 - 65 ) the notorious Nottingham has never made it out of the fermenter.

I leave the brew in the fermenter for 2-3 weeks after fermentation is complete to clear up and go right to bottling without a secondary

This is as close to a real open fermentation I would try with any type of bucket..

bosco

Nice tip.
I use a water bottle of 10 liters (2.5 gallons) as a fermenter and it has a lid,
I am thinking in put the lid but not close totally, letting the CO2 go out, after 2 or 3 days I could twist the lid totally and wait for 2 weeks.

I've used thick cheesecloth tied over the top of my bucket. Let it run that way for 5-7 days then just slap a lid on it, let it sit and clear for 1-3 more weeks, transfer, prime, and bottle. Never any problems. I try to do open fermentations when the weather is cooler though, less chance of incident. Also, I've gotten advice not to mess with it too much, if at all. Take that as you will.

MARCELO178 said:

I am thinking in put the lid but not close totally, letting the CO2 go out, after 2 or 3 days I could twist the lid totally and wait for 2 weeks.

Click to expand...

NOT A GOOD IDEA !!!!!!!

I do not know why you want to seal up the beer to begin with??
A slight leak in the lid will not harm your beer and will allow fermentation CO2 as well as off gassing to take place without causing any thing like the following:

Fermentation can take a lot longer than 2 or 3 days...
If you screw or twist your lid on a beer that has not COMPLETELY fermented you are looking to have a major problem. The entire batch will build up pressure and blow your fermenter apart and beer all over the room.

Before sealing your beer in a fermenter, bottles, kegs or whatever container that has an airtight seal fermentation MUST-MUST-MUST first be finished.

Test with a hydrometer and do not attempt closing the fermenter (( WHY?? )) until the specific gravity has stayed stable for at least three days. If you don't have one get one. You could also wait 3 weeks or more to be sure fermentation is complete, but a hydrometer is essential if you want to make beer.

The only time doing what you plan on doing is done is by expert brewers who know exactly what they are doing and know that their kegs can contain the pressure that is created.

OMO

bosco

I know you are right about closing the lid too soon. but I had some bad experiences with contamination and I am a little afraid because fermentation is a process that releases heat, when it is done, it will get cooler and suck some air inside the fermenter, but if you do that i will try too.