How to check impermeability of capped bottles?

[kojinakata]

Hi everyone,

I have a not-so-good bottle capper and sometimes I think it affects the quality of my homebrew. Do you guys know any techniques to check whether air can pass through the cap of the bottle?

Thanks and I wish everyone good brews.

 

[TopherM]

If you put a bottle under water, and it's not airtight, it will bubble.

 

[Vamptrump]

I assume the water test here wouldn't be a good option as you risk adding water to the bottle if it fails. I've read somewhere that if the cap is on tight you can't twist the cap around the bottle. If it isn't airtight then the cap should move. I've never tested this though, so I'm not 100%.

 

[kojinakata]

Thank you for your answers.

I was thinking about the water method, and would be ok I guess if I sterilized the water beforehand. But the quantity of the addition can be a problem, I guess.

Twist method seems like a myth . Just couldn't figure out the physics behind it, but will try it with a bottle of coke if the cap is usable for a coke bottle.

 

[yeahfairly]

If your bottled brews are carbing and holding pressure then your caps should be fine. If your bottled beers are flat with no head retention then you may have a problem. Grab a beer that's been in the bottle for 10 days or longer and shake it vigorously for a few seconds and see if you hear pressure escaping.... if not.. open immediately...... if it gushers all over you and the floor..... caps are good!

 

[charliethebum]

slip a balloon over the cap/down the neck a ways. if it doesn't fill with air after a few days you should be fine

 

[kojinakata]

slip a balloon over the cap/down the neck a ways. if it doesn't fill with air after a few days you should be fine

Will try this with coke inside. I can't take the risk of doing it with brew inside, pressure should be similar although I dont know if it makes a difference. Also when brew is in the bottle, this can point to bad capped bottles. Thanks.

 

[bernardsmith]

If you could put a bottle in a larger container and pull a vacuum from the larger container then the CO2 will bubble in the bottle if there is not a good seal (wine makers use 22 inches of vacuum to degas wines).

 

[snoman6115]

I've tried a couple things early on with twist off bottles. one was add some vinegar to the bottle, maybe a teaspoon. Put about a tsp baking soda in a napkin and crumple it up so it wedges in the neck. Cap the bottle then shake so the baking soda hits the vinegar and it will quickly build pressure. Put the cap under water and look for bubbles. Be very careful as too much vinegar and baking soda can make a lot of pressure and possibly explode. Small amounts and I never had an issue

 

[KartRacer54]

If the cap is leaking it will shows signs when inverted after slight shaking.

 

[DurtyChemist]

If the bottle is bubbling it will be releasing air and not letting in water. Unless you're holding it underwater long enough to let the neck fill up with water I wouldn't worry about it. My brew shop sells caps to prevent oxidation. Checkout www.brewchatter.com for their bottling caps.