# What's The Psi Within A Homebrew Bottle?



## BjornJ (7/8/09)

I have been reading with interest the tests several of the guys here have done about pressure testing their cubes.
The consensus seems to be that 10 PSI means round as a balloon, 3-5 PSI would be ok for repeated use.

But what does that mean in practical terms?

Is there anyone who knows what the pressure would be within a "standard" bottle as in a 740 ml Coopers PET bottle of homebrewed ale naturally carbonated using 2 carbonation drops?



thanks in advance if there is anyone with the equipment and time to test,

Bjorn
(Asking of course for how much pressure a cube would have to be able to withstand to be use to fully carbonate beer)
(while enjoying a Coopers Mexican with some specialty grain that is just not right. Definetly not right. Better empty the bottles so I can make something else)


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## Nick JD (8/8/09)

I've heard 2 and a half volumes of CO2 in a bottle thrown around. 

So 750ml x 2.5 is 1875ml. One atmosphere is 15 psi, so times 15 by 2.5.

Just guessing though.

I did see something on mythbusters where they put 100+ psi into PET bottles no worries.

BTW - a cube may well hold "standard" carbonation, but will it hold it reliably - that'd be my concern.


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## buttersd70 (8/8/09)

2.5vol is fairly common carb level, but 2 carb drops are more likely to be around 2.9-3vol. The acual pressure this equates to depends on the temperature...the co2 goes into, and out of, solution, equalising due to it being a closed system. lets say it's 2.9 vol....
@ 4C, it would have 16.1psi pressure. @8c, 20.4psi. at 15C it would be 28.2psi.....I lost my chart that goes higher in temp....but from previously working out pressures required to carbonate kegs naturaly (which basically is the same thing as what your asking with bottles  ) iirc 25C works out about 40psi, or just under.

edit: in terms of cubes, though....some of the IBU guys do it for real ales, but bear in mind that the carbonation level on that is _really _low, like 1.2-1.7 volumes of co2. Proper English low. Your prior attempt was probably not far off that....in fact, if you'd had the beer at 9C when serving, and hit it with a 'pocket sparkler', it probably would have been bang on.


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## RdeVjun (8/8/09)

We use these for surface and groundwater level at my work. Well actually not these particular Van Essen Divers, we had a few problems with them and we now use the Solinst range, but I don't think any manufacturer has one quite as skinny as this MicroDiver, 18mm:






So what do they do? Well, they're a sealed/ non- vented pressure transducer and logger in one enclosure and they measure and log absolute pressure and temperature, while comms is achieved through an optical interface through a window (under the black cap which is unscrewed off the top). They would be ideal to monitor the carbonation process for pressure and temperature in a sealed container if they can fit through the neck prior to sealing. Only thing is, you would have to open the bottle up to actually download the data and then normally we would perform barometric compensation, but that's no biggie- BoM data would probably be fine for this sort of experiment, and maybe not even necessary at all in this sealed application.

We use them quite a bit as they're a self- contained sensor and logger, they're very unobtrusive, relatively cheap, quite accurate and versatile, plus can be easily suspended in our 2" monitoring bores. Being absolute pressure, barometric compensation is necessary for accurate water level data, but no problem for us as we have barologgers spread across each network. Its far simpler now to equip a monitoring station with these, there's no need for a hut or logger box/ enclosure, power supply/ solar panels or stilling well, so makes it much easier to equip a station, be it surfacewater or groundwater. Oh, and no, I'm not a salesman, nor affiliated etc...

We have experienced very aggressive groundwaters which corrode even stainless, or more to the point, the actual sensor diaphragm, but have found in situations like that, and I'm thinking beer approaches this, an ordinary condom is an excellent protective sheath when knotted at the opening after putting in some plain water to transmit the pressure signal along with the logger inserted snugly inside. This protection obviously excludes use of water quality sensors though, i.e. no use for the most expensive EC models (>3000 clams).

If cube pressure is what you want to measure with one of these, then there'd be no need to go for the skinny one, the one pictured above would however fit into a PET or a glass bottle as well. The skinny ones are probably around 1000 clams each though, maybe even more, but I already have the comms interfaces and a few baros. There's also the OneTemp range, with prices too, but all of these makes I mention here would probably be out of the price range of most hobbyists. I know some firms might provide a few on loan for 'evaluation' though.


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## BjornJ (8/8/09)

Those pressure sensors look cool, but seem a little out of my budget  

Maybe you could borrow one from work for 2 weeks and put one in a carbonating homebrew bottle, hehe.

There is definitely something I don't understand here?

Atmospheric pressure at sea level is approx 14.7 PSI like Nick said, I just looked it up.
What the ^^?
But how does this fit with the guys on the forum showing that when putting 10 PSI in a cube it looks like a balloon?
Does that messure in addition to the "standard" pressure, not actual pressure?

thanks
Bjorn


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## Nick JD (8/8/09)

BjornJ said:


> Those pressure sensors look cool, but seem a little out of my budget
> 
> Maybe you could borrow one from work for 2 weeks and put one in a carbonating homebrew bottle, hehe.
> 
> ...



There is a fifteen pound collumn of air on top of every square inch of sea level area. 

Put ten psi into your cube and take it to the top of Everest ... it'll have how much pressure in it then?


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## RdeVjun (9/8/09)

BjornJ said:


> Those pressure sensors look cool, but seem a little out of my budget
> 
> Maybe you could borrow one from work for 2 weeks and put one in a carbonating homebrew bottle, hehe.
> 
> ...


Ok, basically its the additional or relative pressure you're needing to consider there. When the cube is first sealed its relative pressure is zero, so no different to the atmosphere, then adding 10psi is just that, additional relative pressure. Its absolute pressure would be something like 14.7 + 10psi.
What you'd normally measure with say a pressure gauge is the relative pressure. I think about it as a diaphragm (which it often is), i.e. the backend of it is vented to the atmosphere, the front to the fluid and the measurement is the deflection of the diaphragm. Because the sensors like the one above are sealed and not atmospherically referenced, they're measuring absolute, not relative pressure.

Yeah Bjorn, if we had some of that skinny micro model at work, I'd gladly borrow them myself actually, its an ideal and novel application for them and would be much more interesting than just boring old water levels when explaining their function to folks. I did a presentation at a hydrographic/ water monitoring conference a couple of years ago on these gadgets when they were new and the unusual condom application got a rise, I reckon they'd have been salivating and getting really barred- up if I'd mentioned the beer carbonation logging application as well. Mind you, the stereotypical hydrographer is a single, middle- aged man who invariably drinks like a fish, so a mention of anything to do with sex or beer will get his attention. BTW, I'm not actually a hydrographer, but a closely- allied techo & dba, and there's a few homebrewers amongst the ranks.

Hmm, now I think I might just be asking Van Essen's distributors for an evaluation unit or two so I can include this novel application in my conference/ training presentation (I do two or three a year), but also to provide some answers for our bretheren. It'd plug their skinny product too, some other models have been dented quite badly of late by way too many failures. I'll ask around our dept too, someone else might've got some microdivers already.
We've got Butters' pressure data already (BTW many thanks for your assistance, Butters), and 40psi is about 28m of H2O, so I'll probably just get the 100m range one to include a margin for error.
We could do PET without enclosing a diver in it, being plastic, the screw lid is slightly more amenable to pressure fittings, albeit with a very limited space to work in, but introducing extra headspace with tubing to a sensor could be an issue I'd expect.
I'll let you know what I can turn up, with any luck we can do some of this and answer a few questions.

Oh, and Bjorn, did you post about the Coopers English Bitter tin a few months ago? If so, how did it turn out? I did one and was reasonably happy, but I partial mashed some more malt and specs plus added some styrian goldings for flavour and aroma as well, so it wasn't really a fair test of just the tin. No complaints though, I would buy that tin again.


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## BjornJ (9/8/09)

Wow, thanks for the long and detailed answer!
Reassuring to have an expert around, maybe I should post the details before trying any more pressure related experiments for your review. That would probably be a lot safer!  

Coopers English Bitter:
I really liked the coopers bitter. It's the first bitter I had ever tasted, so I am probably not the right person to judge it. But for someone used to drinking "light-colored" beers, I thought it was brilliant. I only used the LDME as suggested and dryhopped with a teabag of fuggles. I would definitely not mind doing that beer again. It has a darker, maltier taste than what I normally drink (and more bitter, hehe) but still light enough to drink like a normal beer, not the thick sirupy feeling stout gives me some times.
After my first try on an AG a little while ago and hanging around helping out while a mate made another AG yesterday, I am thinking of keep trying to do more AG before doing another can. It was surprisingly easy with only a 20 liter pot from BigW and a grain bag.


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## RdeVjun (9/8/09)

BjornJ said:


> Wow, thanks for the long and detailed answer!


Sorry, I do get carried away with essays...


BjornJ said:


> Reassuring to have an expert around, maybe I should post the details before trying any more pressure related experiments for your review. That would probably be a lot safer!


Really? So where's this expert then?  In all seriousness, its partly what I do for a crust, so I have to get across the kit and also the concepts. Fire away though, if its out of my league, I'll defer to someone with the bigger brain.
We'll have to see how we go with getting an 18mm diameter Microdiver, they may not play dice in which case it'll just have to remain out of my reach. As I relate, it would make my training and professional presentations a tad more interesting if I could 'evaluate' one.


BjornJ said:


> Coopers English Bitter:
> I really liked the coopers bitter. It's the first bitter I had ever tasted, so I am probably not the right person to judge it. But for someone used to drinking "light-colored" beers, I thought it was brilliant. I only used the LDME as suggested and dryhopped with a teabag of fuggles. I would definitely not mind doing that beer again. It has a darker, maltier taste than what I normally drink (and more bitter, hehe) but still light enough to drink like a normal beer, not the thick sirupy feeling stout gives me some times.


Good, me too. I'd try it again if need be. But...


BjornJ said:


> After my first try on an AG a little while ago and hanging around helping out while a mate made another AG yesterday, I am thinking of keep trying to do more AG before doing another can. It was surprisingly easy with only a 20 liter pot from BigW and a grain bag.


You're right, BIABing is just so simple and I'm actually mashing right now with exactly that equipment, while up until now I have turned out some fabulous ales, even if I do say so myself. A few disasters as well, but not because of the mashing method. I even did a larger- sized batch of around 21L yesterday, it can be done with the smaller stockpot- over 4kg of grain, like a traditional three- vessel system's batch, just a thicker mash, sparge/mashout and dilution of the wort at the end. Today I've even incorporated a protein rest for a lager (I don't usually do lagers), and most of these sorts of process can be done with BIAB, so its a really simple and cheap way to get into AG and also produce terrific results. Some folks may object, that's fine, but I'll keep doing what produces the results for me. Like I've said before, the two Rheem firkins (i.e. kegs, legally- owned of course) I have on hand for setting up a traditional system I'm in no hurry to modify and kit out as BIABing seems to do pretty much all I really need. Oh, and as we all now know, with the depth of knowledge, extraordinary skill and precision some of our colleagues here possess, the results can indeed be award- winning!


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## BjornJ (10/8/09)

When I did it I only made a half-batch, after loss to kettle, fermenter and cube I ended up with 8 longnecks. A lot of work for so few beers!  

I have been playing around with the idea of making a normal sized batch by making a high OG wort and dilute in the fermenter with water to the desired OG.
But is this as easy as in Beersmith make a 23 liter recipe and say mash in 2.5 liter/kg of grain, then rather than sparge just use cold water in the fermenter until I hit the desired OG?

I have read somewhere that hops prefer boiling at 1040 (the reason escapes me) but if people make really "big" beers there should be nothing wrong with boiling in a thicker wort and diluting, I hope.

thanks
Bjorn


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## BjornJ (10/8/09)

RdeVjun said:


> Really? So where's this expert then?  In all seriousness, its partly what I do for a crust, so I have to get across the kit and also the concepts. Fire away though, if its out of my league, I'll defer to someone with the bigger brain.
> We'll have to see how we go with getting an 18mm diameter Microdiver, they may not play dice in which case it'll just have to remain out of my reach. As I relate, it would make my training and professional presentations a tad more interesting if I could 'evaluate' one.




Forgot to ask the question, just rattled on off-topic!

Years ago when I played paintball in Norway, we used this white teflon tape to keep things non-leaking. Gas bottles and that kind of thing.
If I get some of that tape and put around the threads of my cube tap and on the cap itself, do you think the cube will hold the pressure of "normal carbonation" ?
Not low-carbonated real ale kind of stuff, but throwing a fermented beer in there with quite a bit of dextrose.
(I understand the teflon tape will not make the cube any stronger. I think the CO2 escaped through the tap in my last test, after some brown stains under the tap)
If the cube bursts I am not all that worried, just want to try again towards SedimentFreeHomebrew.

Bjorn


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## RdeVjun (10/8/09)

Mate, I seriously think there's enough variability between cubes and taps/bungs for it to be academic. If you feel you need to use PTFE tape, then by all means go for it, but I'm not sure it will stop your carbonating brew spitting out a fitting or 'throwing a leg out of bed' to poach mechanics' terminology. It should't hurt, so long as you're OK with the sanitation aspect (its a prick to wind on cleanly), and I've heard of folks using it, but I would ask myself if its structural or just for convenience. The oragney/pink version might be better, its much thicker (less turns of it).
I have a fermenter that is a touch loose in the thread and am tempted to use PTFE tape, or just use it for primary (tap angle is unimportant, not for bottling) from now on, it seems to jump thread around 5:55PM on the dial, if only I could get it that fraction more of a turn it'd be perfect.
Also, you've tried crash chilling, gelatine, polyclar etc? I find that gelatine, and few days or so in the fridge calms enough of my ale sediment down, but I'm not particularly fussy about sediment or debris either and there's always some of that. No way can I drink them straight from the bottle. An extra week in primary plus gelatine is enough for my ales, hardly even go to secondary these days, but I'd also acknowledge that some of them, plus most lighter- coloured ales and lagers, would benefit from reduced sediment. It could also be that your water might do with some balancing, I just know, once again from my work, that chemistry will have an impact on turbidity and flocculation, and so will temperature cycling.

Now, with the 19L stockpot/BIAB and diluting wort, I've done a few close- to- full- sized batches (21L into the fermenter) with this kit. It seems to work well enough and can be done, while I'm constantly amazed at the efficiency, but that's with a sparge/mashout phase, and I did one batch like this just yesterday. I get ~3/4% of the first lift runnings' SG in around 5L of sparge, so when you start with <4kg of grain, it gets very close numerically to the more traditional mashing methods and boil volumes. 
Yes, the wort is very concentrated, I get a pre- boil SG well over 1.05 quite often, and there may be reasons why this is not ideal, but so far I've found it works OK (he says, sipping the results...). I've done this with ales and have lagers underway at present to confirm it, but so far so good. It may well get some knocking, but so far it works well enough for my needs, although I won't for a minute pretend that I'm an expert at this brewing caper. 
If you don't want to push the envelope so far then there's always smaller batches or partial mashes by adding extract to the fermenter. I've been tempted to do three BIABs into two 23L batches but consistency is one issue I've not overcome, but that's largely my mad scientist at work there- I am a bit of a non- conforming flibberty- gibbert when there's a recipe and method laid out in front of me.

Oh bugger, there's another stinking essay... A thousand pardons...


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