Worried about glass bottles

[GerbilFX]

I have a batch which I'm about to bottle. I've used 1.25L plastic soda bottles in the past. I fill them to about 80% full with the recommended amount of sugar for a 750mL bottle in each. I squeeze the bottle so that the liquid almost reaches the top then put the cap on tight. This minimizes the O2 in the bottle and allows it to expand to its original volume as CO2 builds.

I want to use some glass bottles. But glass can't be squeezed or expand. In order to carbonate, the CO2 must displace something (either air or beer). With nowhere for the displaced air or beer to escape and no way for the bottle to expand its capacity, my limited understanding of physics says that a glass bottle is destined to explode.

Can someone explain exactly how glass bottles carbonate without exploding?

 

[Revvy]

Read this... https://www.homebrewtalk.com/f14/bottling-growlers-instead-bottles-211931/#post2485996

Nothing is being displaced really in bottling. Co2 is being created and forced into liquid....

And the bottles are rated to contain the pressure of carbonation without exploding. Though all bottles aren't that's why we don't bottle in wine bottles or recommend using growlers. And for some beers we need to carb in champagne bottles or belgian bottles which are stronger.

 

[GerbilFX]

Ahhh..... I think I see it now.

The CO2 saturates into the beer and the air above it. Obviously air and beer, being gas and liquid, are not occupying all the space inside the bottle. There are spaces between the molecules that the CO2 can find a home in.

As the amount of CO2 increases, the outward pressure exerted by the bottle's contents rises as they try to push out and return to their natural pressure and density. With nowhere to go inside the bottle, the contents simply remain in a denser form, until you open the bottle.

So a bottle will only explode if the amount of CO2 produced is too high and causes the contents to push out the bottle with more pressure than the glass can handle.... hence: breach.

Thank you for enlightening me.

 

[ChshreCat]

+1 Pressure is created, but that's the whole point. You can't have carbonation without pressure and the bottles are designed to hold the pressure.

By squeezing the plastic bottles, you were actually working against yourself. The yeast had to produce enough CO2 to make up for the pressure you applied from the outside before it could even start carbonating the beer.

As the co2 builds up in the headspace int he neck of the bottle it's that pressure that causes the excess gas to be forced into suspension in the liquid causing carbonation.

In a kegging system the same thing is done by forcing CO2 into the keg until it is at a high enough pressure that the gas goes into the liquid.

 

[GerbilFX]

By squeezing the plastic bottles, you were actually working against yourself. The yeast had to produce enough CO2 to make up for the pressure you applied from the outside before it could even start carbonating the beer.

As the co2 builds up in the headspace int he neck of the bottle it's that pressure that causes the excess gas to be forced into suspension in the liquid causing carbonation.

Good point. I only do it because it was recommended to me as a precautionary measure. My last brew ended up very well carbonated. The bottles were hard as rocks when they were ready, despite using only 2/3 the recommended amount of priming sugar.

 

[ChshreCat]

Revvy has a thread on "everything you wanted to know about bottling but were afraid to ask" that he'll share with you if you say please. No... forget that... you don't have to say please. He'll post the link with every opportunity.