Use PET bottles to determine carbonation?

[sablesurfer]

Hello,
On the face of it, one of the brewers in my club suggested something that was pretty brilliant. If you need to check/test carbonation levels but do not want to open a bottle ever day, why not use a PET bottle and that way you can just squeeze to test for carbonation.

This is important to me now, for two reasons:

1) I only have a gallon of this experiment and opening a bunch of bottles too early would ruin the point of making my first ever cider.​

2) I am attempting to bottle condition a 'sweet' cider and need to follow the steps of 'bottle, let carb, then pasteurize' for this one.​

However, as of this morning (one day after bottling) the PET bottle already feels just as pressurized as it did when it had soda in it. So I am wondering if there really is any leeway in when you could tell just by hand squeezing. I would never expect a beer to have carbonated this quickly. Or, would bottling it before FG mean it carbs faster?

Anyone tried this?

 

[LeftyRighty]

I have bottled 1/4 to 1/2 of my brews in 12oz PET bottles, for friends or to take for visits - don't need to worry about collecting glass bottles later.

When filling, I squeeze the bottle a bit to expel last bit of air as I put the cap on, this leaves a dent in the PET bottle. Within a couple of days, the dent is gone - so I know I'm getting carbonation. Usually, within a week, the PET bottle is near rock-hard, almost impossible to squeeze - that's when I know I got full carb.

 

[HaDaL]

I've used a PET bottle along with glass bottles in the past but not for what You mentioned.I did this to prevent the beer bombs when I was brewing some styles with high level carbonation and I was suspected glass bottles can not withstand the high gas pressure.If PET bottle was swelled or deformed somehow,I was realizing that I might pay attention to glass bottles before they explode.I think You can not find the proper carbonation time in this way because We know, initially gas is produced,then comes out of beer and is collected/compressed in the empty space of bottle,then comes back to beer and will be dissolves there.This cycle continues until equilibrium is established between the liquid and the space above it.Here is when We can say that the beer is carbonated.In other words, hardening of pet bottle only indicates that gas is produced and It dose not mean that beer is carbonated too.

 

[ol-hazza]

Have a look at this thread, its working on the same principal but slightly more high tech.

https://www.homebrewtalk.com/f51/pressure-gauge-mounted-bottle-cap-268151/