The topic says it all - how much do i fill my 2 litre PET bottles?
My primary fermentation has finally ended after 19 days.
Gonna bottle with tesco PET bottles.
2 Litre PET bottles how full??
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Madbrewer
Assuming that you are bottle conditining?
Leave 1.5 - 1.75 inches free at the top of a two litre bottle. Bt thta i mean measure from the bottom of the screw thread and not the top.
Also before screwing the cap on, squeeze the air out and seal squashed so the co2 can expand the bottle rather than having excess Oxygen/ air in there.
A Word of warning though - the 2 litres are difficult to decant without disturbing the yeast.
Leave 1.5 - 1.75 inches free at the top of a two litre bottle. Bt thta i mean measure from the bottom of the screw thread and not the top.
Also before screwing the cap on, squeeze the air out and seal squashed so the co2 can expand the bottle rather than having excess Oxygen/ air in there.
A Word of warning though - the 2 litres are difficult to decant without disturbing the yeast.
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johnh
From what I understand you want to get all that air out of the bottle for various reasons:
1) The suspended yeast has been happily working anaerobically for at least a week. It will be reluctant to go back to aerobic activity and even if it does then budding will be encouraged leading to unwanted by-products and extra sediment in the bottle.
2) Oxygen is known to produce staling reactions.
2) The presence of oxygen will be helpful to any aerobic bacteria that happen to have got into the beer.
On the other hand it's probably a stupid question but can someone tell me why you don't just fill a PET bottle up to the brim?
1) The suspended yeast has been happily working anaerobically for at least a week. It will be reluctant to go back to aerobic activity and even if it does then budding will be encouraged leading to unwanted by-products and extra sediment in the bottle.
2) Oxygen is known to produce staling reactions.
2) The presence of oxygen will be helpful to any aerobic bacteria that happen to have got into the beer.
On the other hand it's probably a stupid question but can someone tell me why you don't just fill a PET bottle up to the brim?
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MacDuck
I dont really know, but air (or any other gas for that matter) is much more compressable than a liquid. Perhaps It has something to do with possible expansion of the liquid due to heat (or more likely freezing) - although the liquid should not expand much at all.. anyway, should the liquid expand then the air/gas gap can easily be compressed to give the liquid space... else bottle go boom?johnh wrote:On the other hand it's probably a stupid question but can someone tell me why you don't just fill a PET bottle up to the brim?
just a laymans theory
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johnh
Perhaps It has something to do with possible expansion of the liquid due to heat (or more likely freezing) - although the liquid should not expand much at all.. anyway, should the liquid expand then the air/gas gap can easily be compressed to give the liquid space
When the temperature increases the gas compresses because it's under greater pressure. In the end it's the pressure in the bottle is what makes it go bang. I find freezing beer bottles makes them go bang whether there is a head space or not!-
stevezx7r
I don't think haveing any head space in PET bottles makes any difference (one way or the other). PET bottles can take way more pressure than you would normally find being produced by beer but glass beer bottles are more likely to break.
I think it's just a method carried over from bottling beer in glass bottles - leave an inch gap for the CO2.
I think it's just a method carried over from bottling beer in glass bottles - leave an inch gap for the CO2.
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Madbrewer
I think it comes from the bottling procedires for glass bottles. I.e. You can compress a gas but you can not compress a liquid. The Glass bottle is more likely to explode with no 'gap' to soak up the gas. Therefore allowing some 'gap' for the co2 to work without blowing the lid off seemed (to me) to be a good idea.DaaB wrote:I'd like to know this also.On the other hand it's probably a stupid question but can someone tell me why you don't just fill a PET bottle up to the brim?
Also Daab the idea of squeezing the bottle may or may not be a good idea, but minimising the (possible) oxygen [Seemed] like a good idea to me. However as previously discussed my bottling procedure in PET's definetely leaves a little to be desired in terms of disturbing the yeast at the bottom and in terms of syphoning back out of PET's & not getting a syphon tube full with foam.
Am happy to relent on both points to your superior (brewing) wisdom if you think my advice is bad though?
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CyberPaddy66
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CyberPaddy66
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dreadstar
I'm gonna bottle into some of these for my TC just thinking about decanting and I'm guessing the issues you are having are due to air trying to get back into the bottle to fill the void you have created by pouring beer out and these big bubbles of air disturb the sediment in the bottom of the bottle. How about if you stick a straw or some siphon hose out the top to allow the air into the bottle in a more controlled way whilst pooring?Madbrewer wrote: However as previously discussed my bottling procedure in PET's definetely leaves a little to be desired in terms of disturbing the yeast at the bottom and in terms of syphoning back out of PET's & not getting a syphon tube full with foam.
On the gap issue, is it not better to have no air/oxygen in the bottle and let the it refill the space with CO2 eventually building pressure once the void has been filled? Maybe adding a little more priming sugar? I'm tempted to just fill my to the brim and pray for the best. I know I have had some Coke bottles in the past pressurised to hell after dropping etc and they haven't blown
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sparky Paul
I have a little experience of commercial bottling, and I think I might be able to able to help you out with the theory behind this.
There are two main reasons for the inclusion of headspace in carbonated bottles. First of all, it is to allow for inconsistancy during filling, to ensure that none of the contents overspill onto the threads. If the contents had some sugar content, then the bottle may become very difficult to open, encouraging the use of tools to open it. Secondly, the headspace allows for a small area of compressible gas to allow for liquid expansion caused by changes of temperature.
That's it really. For commercial PET production, the target is normally 4% headspace by volume. There are good reasons for this. If the headspace is too small, bottles or closure (cap) may rupture under extremes of temperature. However, too large a headspace increases the volume of compressed gas, which in turn dramatically increases the ballistic force of a missiling cap, if it were to rupture under extreme pressure.
For homebrewers, you're going to be okay unless you ridiculously over-prime your bottles, or if fermentation was incomplete when bottling. Don't fill to the brim, and take care if you underfill, I would actually recommend reducing priming sugars in that case. I would say try to aim for a similar fill to that of commercially filled bottles, that's what I do anyway.
If you fill to the brim, you will find that little space is created by escaping CO2, certainly a lot less than 4%. Once the bottle has expanded to it's limit, no further CO2 will come out of solution, pressure will just start increasing - something to do with Boyle's Law, IIRC. I know this sounds odd, but squeezing air out of a bottle of carbonated drink before replacing the cap actually prevents CO2 coming out of solution and stops it going flat.
In any case, will the activity of the yeast will scavenge some of the oxygen in the headspace?
There are two main reasons for the inclusion of headspace in carbonated bottles. First of all, it is to allow for inconsistancy during filling, to ensure that none of the contents overspill onto the threads. If the contents had some sugar content, then the bottle may become very difficult to open, encouraging the use of tools to open it. Secondly, the headspace allows for a small area of compressible gas to allow for liquid expansion caused by changes of temperature.
That's it really. For commercial PET production, the target is normally 4% headspace by volume. There are good reasons for this. If the headspace is too small, bottles or closure (cap) may rupture under extremes of temperature. However, too large a headspace increases the volume of compressed gas, which in turn dramatically increases the ballistic force of a missiling cap, if it were to rupture under extreme pressure.
For homebrewers, you're going to be okay unless you ridiculously over-prime your bottles, or if fermentation was incomplete when bottling. Don't fill to the brim, and take care if you underfill, I would actually recommend reducing priming sugars in that case. I would say try to aim for a similar fill to that of commercially filled bottles, that's what I do anyway.
If you fill to the brim, you will find that little space is created by escaping CO2, certainly a lot less than 4%. Once the bottle has expanded to it's limit, no further CO2 will come out of solution, pressure will just start increasing - something to do with Boyle's Law, IIRC. I know this sounds odd, but squeezing air out of a bottle of carbonated drink before replacing the cap actually prevents CO2 coming out of solution and stops it going flat.
In any case, will the activity of the yeast will scavenge some of the oxygen in the headspace?
Last edited by sparky Paul on Thu Apr 10, 2008 2:43 pm, edited 1 time in total.
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Madbrewer
The release of the cap seemed to allow the expulsion of gas with sufficient force to 'pull' the yeast from the bottle bottom. I put this down to over priming.dreadstar wrote:I'm gonna bottle into some of these for my TC just thinking about decanting and I'm guessing the issues you are having are due to air trying to get back into the bottle to fill the void you have created by pouring beer out and these big bubbles of air disturb the sediment in the bottom of the bottle. How about if you stick a straw or some siphon hose out the top to allow the air into the bottle in a more controlled way whilst pooring?Madbrewer wrote: However as previously discussed my bottling procedure in PET's definetely leaves a little to be desired in terms of disturbing the yeast at the bottom and in terms of syphoning back out of PET's & not getting a syphon tube full with foam.
The problem regarding a syphone full of foam I put down to a mix of i) too much carbonation (perhaps) AND ii) not cool enough - therefore the combination of these factors casuign a forcing of co2 bubbles out of suspension in the syphon tube.
I either need to practice more or put it to rest as a bad idea with my set up. The Ability to keep going with PET's is quite attractive though if i get it sorted.
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MightyMouth
I have only bottled kit cider in PETs but I filled them right up to the top with a little bottler so when I took the Little bottler out there was a little headspace but not much. These turned out perfectly carbonated and the yeast sediment at the bottom wasn't a problem at all until the last 1/4 pint and even then I got very little in the glass.
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sparky Paul
Releasing the pressure in the bottle allows CO2 to come out of suspension, and it forms on particles of yeast, pulling them up to the surface.Madbrewer wrote:The release of the cap seemed to allow the expulsion of gas with sufficient force to 'pull' the yeast from the bottle bottom. I put this down to over priming.
The problem regarding a syphone full of foam I put down to a mix of i) too much carbonation (perhaps) AND ii) not cool enough - therefore the combination of these factors casuign a forcing of co2 bubbles out of suspension in the syphon tube.
I carbonate lagers more, and have to refridgerate them or else...