[Silicon]

Has anyone ever found or made bottle tops which let CO₂ escape beyond a certain PSI level? I'm thinking something like a pierced cork, probably rubber or plastic, not cork wood, and likely having a hole piercing it. Maybe someone even better?

Or has nobody ever seen anything like this before?

I'm experimenting with some wine corks right now. If something works, I'll post back. (Hey, you never know!) What I'm trying is piercing corks with different shaped holes (slits), hoping to find just the right shape which lets gas pass through but only at a certain pressure level. Yeah, I know it's unlikely that I'd get 2 corks in a row that'd have consistently equal holes, but I thought it worth trying anyway.

From a manufacturing standpoint, I imagine the "hole" technique would be hard to perfect, not to mention being able to sanitize them for re-use, hehe.

[ethinson]

The problem from a physics standpoint is that the pressure in the bottle is always going to be higher and pushing out.  If the bottle starts at 3 volumes and is pushing out, it's not just going to magically stop when it gets to 2 volumes.  It will push out until it matches the outside environment.  At that point there may not be enough pressure to prevent air and bacteria from getting in and ruining your beer.

On a practical standpoint... why? This serves absolutely no purpose.

[Robert]

^^^^^
It not only serves no purpose, it defeats your purpose. You are forgetting your gas laws.  Pressure and volumes of CO2 are not the same thing, they two of three sides of a triangle.  Pressure, TEMPERATURE, and volumes of dissolved CO2 are all interdependent.   So a simple change in any one will require at least one of the other two to shift in order to restore equilibrium.   This is why you must do precisely the opposite of what you propose:  Carbonate beer to the desired level, then seal in a container that will not permit CO2 to escape or other gases to enter.  Then equilibrium will be maintained at your desired level of carbonation despite changes in temperature of the bottled beer.  The variable that will change is the pressure in the headspace in the bottle, not the volume of dissolved CO2.

[joe_meadmaker]

I think if you're piercing a hole in a cork it will be almost impossible to get an accurate pressure level.  What you need is a cap with a pressure release valve.  There are small valves on some fermenter caps.  You can see one here: https://www.norcalbrewingsolutions.com/store/Speidel-Ball-Lock-Gas-In-with-Pressure-Relief-Valve.html.  But you would also need a spring that will be compressed at a pressure just above what you would like inside your bottle.

I haven't seen a valve like this on a bottle cap, but you could probably rig one up.  But as Rob pointed out, the pressure inside the bottle will change depending on what the temperature is.  So as your temp goes up, the valve will let out more CO2.  Agree with the guys, I don't see a use for this on just a single bottle.

[steamyb]

Google Pat Mack's Homebrew Caps. He sells yeast and pressure releasing caps that fit 2 liter bottles and it's basically jail house hooch, but it works. I have used these for years to make fruit wines. I don't know how they would work with beers (I used to keg all my brews).

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[ethinson]

Google Pat Mack's Homebrew Caps. He sells yeast and pressure releasing caps that fit 2 liter bottles and it's basically jail house hooch, but it works. I have used these for years to make fruit wines. I don't know how they would work with beers (I used to keg all my brews).

Sent from my Moto G (5) Plus using Tapatalk

Jail house hooch is right.. he intends for you to drink that while it's still fermenting, so that's how it keeps positive pressure in the bottle. Some bleeds out but it stays "carbonated" mostly because it's still going.  Add yeast and then drink in 3 days? I mean.. it'll get the job done but probably make you sick too from all the yeast in solution.

[Silicon]

^^^^^
... You are forgetting your gas laws.  ...

That would assume that I ever heard of gas laws besides not being able to pump your own gasoline in the whole state of Oregon. (And New Jersey, I believe.)  I'm a software engineer who's learning home brewing. While I've been designing & building software systems for 40 years, brewing beer's kinda new, which is why I'm asking questions in the first place.

So not forgetful, just ignorant, as in "not yet learned". But that's why I'm here.

I'm trying to think of alternate ways of controlling carbonation, e.g. using natural carbonation while reducing the chance of over-carbonating.

PS Some day, I'll be able to afford kegging. Until then, it's bottling all the way! I'll still always do some bottling, just not all of each batch.

[Robert]

^^^^^
... You are forgetting your gas laws.  ...

That would assume that I ever heard of gas laws besides not being able to pump your own gasoline in the whole state of Oregon. (And New Jersey, I believe.)  I'm a software engineer who's learning home brewing. While I've been designing & building software systems for 40 years, brewing beer's kinda new, which is why I'm asking questions in the first place.

So not forgetful, just ignorant, as in "not yet learned". But that's why I'm here.

I'm trying to think of alternate ways of controlling carbonation, e.g. using natural carbonation while reducing the chance of over-carbonating.

PS Some day, I'll be able to afford kegging. Until then, it's bottling all the way! I'll still always do some bottling, just not all of each batch.

So, the best way to  bottle carbonate without over carbonation is just to 1) make sure fermentation has finished before bottling -- a reasonably good indication is if there is absolutely no change in specific gravity over 3 consecutive days -- and 2) prime with the appropriate amount of sugar when bottling.  There are a lot of charts out there that can tell you how much corn sugar or other sugars you need to achieve a given level of carbonation in a given volume of beer.  Sorry I don't have a link, but you should be able to find the info.  John Palmer's How to Brew is a great source on this topic.

PS I didn't really know gas laws as a result of formal training or occupational experience.  I've learned a heck of a lot of science and other cool stuff in the course of brewing.   One of the cool things about this hobby, if you are so inclined!

[ethinson]

^^^^^
... You are forgetting your gas laws.  ...

That would assume that I ever heard of gas laws besides not being able to pump your own gasoline in the whole state of Oregon. (And New Jersey, I believe.)  I'm a software engineer who's learning home brewing. While I've been designing & building software systems for 40 years, brewing beer's kinda new, which is why I'm asking questions in the first place.

So not forgetful, just ignorant, as in "not yet learned". But that's why I'm here.

I'm trying to think of alternate ways of controlling carbonation, e.g. using natural carbonation while reducing the chance of over-carbonating.

PS Some day, I'll be able to afford kegging. Until then, it's bottling all the way! I'll still always do some bottling, just not all of each batch.

In my experience, so your mileage may vary, I've had more trouble/issues with batches getting undercarbed than overcarbed.  Maybe I go light on the sugar? I'm not sure. I've only ever had one bottle explode on me, so I consider myself very lucky in that regard. The easiest way to curb carbonation would be just to reduce your priming sugar. If the book tells you you need X amount for 2.6 volumes, use slightly less and shoot for 2.4-2.5. You might get dinged in a competition is it's supposed to be high carbed like a Belgian, but for personal consumption it will be fine and you wont have exploding bottles.

I'm slowly collecting the components to be able to keg but I've been bottle conditioning everything for almost 5 years and still enjoy it. People always complain that bottling is a PITA but I don't mind it. All hobbies involve work and a time commitment. It just is what it is.