DIY pressure-release caps?

[gasbag]

I'm thinking about making my own DIY plastic fermentation caps for plastic soft drink (soda) bottles - all the fermentation and carbonation would be in the one bottle. The lid would need to have a form of pressure-release mechanism in place so that a moderate level of CO2 pressure can build up and carbonate the liquid, but when the pressure reaches a certain level, it would escape and prevent the plastic bottle from exploding. There are commercial fermentation caps available, but I have my own DIY design in mind.

What I'm thinking of doing is getting empty soft drink bottles and putting a silicone or (hopefully soft) rubber O-Ring around the neck of the bottle - just below the threads, but above the plastic collar that the lid seals against when done up tight.

Once the O-Ring is in place, I'd then do the lid up very,very lightly, with finger-strength only - not by gripping firmly.

I've searched this Forum looking for similar attempts or advice, but not found anything quite on the mark. Any comments on this?

 

[TheHappyHopper]

I think if you see photos of a fermenter after someone has siphoned the beer out of it to the bottling bucket, you would understand why nobody has tried to do this.

At the end of fermentation, there is a thick layer of dead yeast, hop residue, etc. at the bottom of the fermenter. As long as that stuff isn't disturbed, it will stay for the most part on the bottom of the fermenter - however, you are talking about soda bottles (2 or 3 liter?), which are not going to be poured out in one go - they will be constantly tilted, poured, etc. while serving, so all of that stuff at the bottom of the fermenter would get mixed back up into the beer.

There is also the thick, dark ring around the top of the fermenter where the dead yeast and hop residue cling after the krausen has dissipated - this would look super unappetizing in a bottle that you are going to serve out of, but from what I have read, it will also impart some harsh flavors back into the beer if it gets mixed in again.

And finally there is the fact that if you beer sits on top of the dead yeast at the bottom of the fermenter for long periods of time, the yeast start the process of autolysis, which gives off off flavors as well. Of course if you are going to drink your beer within a month or two, you are probably okay in regards to this.

If you are set on the soda bottle idea, I think I would ferment in one bottle and then after fermentation is done, use a sanitized funnel and another bottle, and pour carefully into the second bottle with priming sugar.

 

[Trollheim]

I find it ironic that you posted this. I have wanted to do something similar selling pre-pasteurized wort in a 2L jug with a cap and yeast at farmers market.

I haven't had any luck sourcing the lid solution.

Mr Bottle Brew does this in Canada at a commercial level doing the same as I described above with pasteurization, a vial of dry ale/lager yeast and a standard cap with a drilled hole and custom insert.

http://www.mbbottlebrew.com