PET bottle squeeze

[Weatherman]

Morning all,

Very new to brewing and am using kits. I read many of the threads posted and see occasional references to squeezing PET bottles prior to capping when filled.

I can’t find a thread that explains why or for what this should be done. I assume it’s to remove all oxygen? What benefits are there?

I’m interested as I currently only use PET 500 ml and 1000ml bottles

Many thanks for any replies

 

[Gwen]

Hi Weatherman,

I am still learning loads myself but I haven't heard of squeezing the bottle prior to capping. I am sure if my answer is wrong someone else can head you in the right direction.

I am assuming you are talking about screwing a screw top cap on once its filled.?

I have not yet used plastic bottles for my wine/cider or beer as of yet but will be having a go at Elderflower fizz when the flowers are out. From what I understand about squeezing the bottle is once you have filled the bottle you can feel the bottle in time become harder to the touch when the carbonation has taken place.

 

[Buffers brewery]

Hi @Weatherman I use 4 or 5 PET bottles per brew as I use a PB for dispensing. The bottles are for easy transport to my son. Anyhow, I squeeze the bottles after filling to exclude as much air and therefore oxygen as possible before screwing the caps down tight. This serves 2 purposes. First indicates carbonation as the bottle recovers it's shape as CO2 is produced. And second by eliminating as much oxygen as possible you're limiting the possibility of oxidation of your beer.

 

[Tess Tickle's Brewery]

Yep - what you are doing is removing the oxygen and effectively squishing the bottle, and capping it while it's still squished. Then as soon as it starts carbonating, the squished bits will pop out and your bottle will start to get firmer. The popping out normally takes around 24 hours (but depends how much sugar you have in there), and in total the whole carbonation should be finished within a week.

 

[GhostShip]

This is actually why I like PET bottles. I always leave around an inch at the top of the bottle and then squeeze the beer to the top and secure the screw cap. This leaves the bottles looking dented and out of shape, but within a couple of days in secondary fermentation, they will regain their original shape and you'll 'feel' the pressure inside the bottle as they go very taut. It's a sure sign that the beer has carbonated.

As others have said, removing any oxygen reduces the risk of oxidation (and possibly, 'home brew twang').

 

[moto748]

I'm less convinced about the "oxidation (and possibly, 'home brew twang')" aspect of it, cos you can't do that with the 90% of bottles that are glass, as opposed to the 10% (say) of PET. So that was a big problem, it would surely show up on the glass bottles? But the squeezing the bottles so they deform and then 'harden' due to carbonation, is useful. Also, if your glass bottles are brown, it's good to have a few clear ones in your batch. I have some of both clear PET and clear glass bottles, and try to include a few in each brew batch.

 

[Weatherman]

Many thanks for all the replies.

Up to now I haven’t been doing this at all but will give it a try at the next bottling which will be the Juicy IPA I currently have bubbling away.

 

[Didge]

All of the above reasons are valid, as exposure to oxygen can introduce an undesireable taste of damp cardboard.

The tactile firming of a PET bottle gives a certain reassurance that carbonation is actually happening. Flicking a tight bottle and hearing it ring like a bell is a good feeling (or am I just weird).

 

[RichardM]

The elimination of oxygen is more important with highly hopped beers. As @moto748 says, there usually isn't a problem with most beers which are in glass bottles.

 

[Buffers brewery]

squishing

I think “squishing” should be adopted as an official brewing term relating to the gentle squeezing of a PET bottle in order to exclude as much air as possible prior to fitting a screw cap.

 

[Gggsss]

In my experience I prefer a ‘squeezed’ PET. Definitely makes a difference in terms of punchy hop flavor (when brewing hoppy pales). My batch is always a mixture of swing top glass and PET, and the PET taste better.

 

[Gwen]

See, even at my age you can learn something every day

 

[JockyBrewer]

I'm less convinced about the "oxidation (and possibly, 'home brew twang')" aspect of it, cos you can't do that with the 90% of bottles that are glass, as opposed to the 10% (say) of PET. So that was a big problem, it would surely show up on the glass bottles? But the squeezing the bottles so they deform and then 'harden' due to carbonation, is useful. Also, if your glass bottles are brown, it's good to have a few clear ones in your batch. I have some of both clear PET and clear glass bottles, and try to include a few in each brew batch.

Crown caps for glass bottles have oxygen scavenging liners which are a big help.

I first noticed oxidation when I bottled some beer in swing tops and some in crown caps and saw the difference. I don't think my bottling technique was the best, but even having refined it quite a lot I couldn't eliminate it entirely, particularly for hoppy beers, until I switched to kegging.