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I wonder if any has ever had this happen. After conditioning a batch of ale, a couple of PET bottles that were already hard from carbonating were put in the fridge. After several days they got soft. When opened they had slight carbonation but not like the others. Bottles seemed tight. Any thoughts?

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It was odd because I really had to struggle to get the caps off.  They were as tight as you could get without busting the threads.  It has baffled me.  I may just stick to glass bottles.  Not sure what to make of this.

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4 hours ago, oldbagobones said:

It was odd because I really had to struggle to get the caps off.  They were as tight as you could get without busting the threads.  It has baffled me.  I may just stick to glass bottles.  Not sure what to make of this.

 

It's never happened to me, but then I have only batched 11 kegs, so far.  I do remember MRB saying something about the 1-3 days in the fridge to lock-in the carbonization AND something similar did happen to me once:  I cooled a bottle in the fridge for several days and when I went to pour it into the two 12 oz bar mugs, the first one seemed semi-flat.  So I recapped the bottle, gave it a single, sharp shake, waited a few moments and opened it to pour the second glass.  I poured carefully but the CO2 exploded in the glass giving me a 4"+ head.  The CO2 was there, it was just locked in tight, I guess?  I hate to recommend you do this, but... it might answer a question about the carbonization.  Good luck.

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4 hours ago, oldbagobones said:

It was odd because I really had to struggle to get the caps off.  They were as tight as you could get without busting the threads.  It has baffled me.  I may just stick to glass bottles.  Not sure what to make of this.

nothing against PET bottles, but they have failed me several times....leaks, flat beer....etc. Glass bottles have always been great. i feel like they provide the best seal. bottle washing is a little work, but i really don't mind doing it. i wash around 50 at a time and hang them on my bottle tree. i have a bench capper which will cap just about any size bottle. i've bought a few cases of glass bottles before, but now i buy commercial beer like sam adams...etc. and reuse the bottles if i need more.

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3 minutes ago, Jdub said:

nothing against PET bottles, but they have failed me several times....leaks, flat beer....etc. Glass bottles have always been great. i feel like they provide the best seal.

 

I wish I hadn't just stocked up on 4 cases of MRB PET bottles, cause I see MRB is now offering glass versions of their 740ml (25os) bottles with crimp-on caps.  I'd be ordering them as I write if I hadn't just bought the plastic ones.  I love the size and I'm glad to see MRB has them now in glass.

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19 minutes ago, McSquirrely said:

 

I wish I hadn't just stocked up on 4 cases of MRB PET bottles, cause I see MRB is now offering glass versions of their 740ml (25os) bottles with crimp-on caps.  I'd be ordering them as I write if I hadn't just bought the plastic ones.  I love the size and I'm glad to see MRB has them now in glass.

For me the 750 in glass would be too big. I generally only drink one glass (1x 12 oz bottle) at a sitting so it would likely go flat  on me without a good stopper. That is another reason I like the PET with screw tops.

I will agree I get the most reliable seal from glass bottles w/crimp on caps, but mostly the PET are OK for me. Also use a bench capper - I think more reliable than hand ones.

I am sitting at 223 😮 LBKs bottled and 2 fermenting.

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21 minutes ago, Nickfixit said:

I am sitting at 223 😮 LBKs bottled and 2 fermenting.

Nick, that is a lot of brewing my friend. congrats. 

 

with the time invested in brewing and waiting and waiting, i'm into risk reduction in areas i can control.

 

i bought a case of 22 oz glass bombers recently and will use 1/2 of them on my next batch shortly and the other 1/2 12 oz. just to shake things up.

 

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3 hours ago, Nickfixit said:

For me the 750 in glass would be too big. I generally only drink one glass (1x 12 oz bottle) at a sitting so it would likely go flat  on me without a good stopper. That is another reason I like the PET with screw tops.

I will agree I get the most reliable seal from glass bottles w/crimp on caps, but mostly the PET are OK for me. Also use a bench capper - I think more reliable than hand ones.

I am sitting at 223 😮 LBKs bottled and 2 fermenting.

We like the two-glass volume of the PET bottles because the wife and I enjoy our glasses of beer together, on the couch, watching Netflix or Acorn.  Twice as much per bottle, half as many to deal with.  But now that MRB offers the same size in glass - well, it's a no-brainer to move to glass.  But not yet, I have to re-stock my extracts, DME's, hops and yeasts.

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When placed in the frig, the bottles SHOULD get softer as the molecules slow down.  But they should not get very soft.

 

It's important to keep beer in the frig for 3 days or longer before opening.  When in the frig, the CO2 is being absorbed back into the beer.  If you don't wait 3 days or more, then you will lose some of that CO2 when you open the bottle.

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The bottles were rock hard when put in the fridge.  After a week in the fridge they did get softer but not like past brews where they stayed hard.  There didn't seem to have much co2 at all, producing very little head.

 

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This looks like  fun blog for students of brewing.

This entry from the  log of a student at Niagara College (in Ontario, Canada) Brewmaster & Brewery Operations Management  2 year brewing course is on carbonation and shows some calculation on getting what carbonation you  want.

https://studentofbeer.wordpress.com/tag/carbonation/

Other pages in this are interesting too.

 

I also found and annotated the chart below showing temperature effect is ~ 1.7:2.7g at atmospheric pressure. But the pressure is higher since the CO2 is retained so more will be dissolved. From room temp, the CO2 pressure will also go down as RB says, which will lessen solubility to some extent but since this is related to absolute temperature (deg K), it is not a huge factor (276:294 in this temp range.)  

 

 

For those really into the math of CO2 solubility....https://www.researchgate.net/publication/277688911_Carbon_Dioxide_Solubility_in_Beer/download

https://tapintohach.com/2013/01/28/co2-solubility-in-beer-does-quantifying-it-precisely-matter/

 

 

CO2_solubility.png

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I like the plastic bottles, but the caps can be problematic. As NicKfixit suggested, the caps may have deformed and leaked. Get new caps. I observed, that at room temperature, the caps on fully carbonated, PET bottles have a very slight convex shape. Once cooled in the fridge they are flat, supporting the idea of a slight deformation. I can't get a good photograph of side by side comparison, but both my sons confirm that it is not an illusion. Anyway, most seem to last about 4 uses, then are shot. I need to order a bunch as I'm past that. BTW Nick - that math hurts my brain - I need a beer.

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I guess I should invest in some new caps.  Ive used them about four times so your analogy seems to fit my situation.  I like the PET bottles because their volume suits my liking.  That being said I may move to the glass bottles and shy away from the PET in the future.  I am considering going into kegging in the future and leaving all the bottles behind.  Thanks for all the insights guys!

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If you get new caps (I go 6 or more times), make sure you remove the old plastic ring from the bottle (snip it off) before putting on new caps, which have a new ring, which then breaks off and stays on the bottle.  Stacking two rings will ensure flat bottles.  

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I have remove the rings from the bottles after first use.  They seem to inhibit a good seal.  When I get new caps I will do that before capping.  Thanks RickBeer that is good advice we should all heed.  Those tamper rings are just annoying.

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2 hours ago, oldbagobones said:

I have remove the rings from the bottles after first use.  They seem to inhibit a good seal.  When I get new caps I will do that before capping.  Thanks RickBeer that is good advice we should all heed.  Those tamper rings are just annoying.

I have left mine on the bottle but always remove before using a replacement cap.

I have reused caps many times. They lose elasticity in the seal after a bit but I will change them if I seem to be getting leak in the carbonation phase (if the bottle is low compared to rest of batch after a week or so). I replace the cap and throw an additional sugar dot in. But generally I think more than 6 times. I can tell by the build up of the labels on the cap. Probably should sterilize the cap too but I am lazy and lucky - no distinctly different bottles in the batch.

 

Note if you drink soda or know anyone that does, the screw caps also fit the Mr Beer PET bottles. Save them, so you can reuse those too (and no annoying rings - 😁).

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