Should I top up low level beer bottles? Beginner's error...

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Jun 4, 2024
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Hi there,

I've been lurking around and reading posts on here for a while now, but really I'm a newbie to beer brewing. I've dabbled in wine making before but I've just turned my hand to the beer... and I think in my eagerness I've gone ahead and made a really stupid error.

I did a fair bit of research (thanks for everyone's posts, this group has been really helpful) in the build up to starting the brew, and read a few things about the dangers of bottle bombs. And yet. Very stupidly, SOMEHOW, I got it into my head without really doing proper research into this (like a huge idiot), that the most important thing to do to avoid bottle bombs was to leave space at the top of the bottle when bottling a finished-fermenting brew. So, I had it firmly in my head not to over fill the bottle. I thought i'd be on the safe side, and leave quite a few inches from the top of the bottle. Of course, I added my 1 teaspoon of sugar to each bottle, and closed them off.

It was only AFTER I'd done all 46 x 500ml bottles, that I questioned myself. I researched more into the gap you should leave at the top, and the consensus was that it only needs to be 1 inch. In fact, it seems that by leaving more space at the top, I've not only opened myself up to oxidisation, but I'm more likely to create bottle bombs! Well, bloody brilliant. I'm a huge idiot.

I bottled them about 18 hours ago, so they've only been newly bottled for about 18 hours.

So, my question is; should I reopen the bottles and top them up to leave only 1 inch at the top. I would have to do this by pouring from one or two of the bottles themselves, as I emptied my whole fermentation bucket in the bottling process. I've used both beer brewing PET 500ml bottles with screw tops, and reusable glass 500ml bottles with swing tops.

Would re-opening and topping up, ruin the beer?

Would the beer in the topped up bottles be able to continue the extra fermentation and create enough CO2 to carbonate, without me adding more sugar? I've heard adding more sugar is also a bit risky.

Would I just be creating more opportunities for oxidisation?

OR .... should I leave the bottles as they are........ is it likely I'll have a ton of bottle bombs? I'm only brewing a very simple cheap IPA kit - I've kept it simple in case I manage to mess up this first batch... which now seems very likely! I'd just be gutted to have a completely wasted batch, because. Well. It's just gutting isn't it?

Would really appreciate any help with this, thanks all. Apologies if this has been asked before, I couldn't see a thread asking this.
I'm not convinced that leaving more space at the top of the bottle increases the likelihood of bottle bombs : bottle bombs can happen in two situations - a) too much yeast consumable sugar in the beer (either from overpriming or fermentation not being complete when the beer was bottled) causing the yeast to produce more CO2 and thus pressure than the bottle can handle, or b) some kind of infection that munches away at the non yeast fermentable sugar and does the same (although bottle bombs are rare in this scenario; over carbed gushers are more likely). Niether of these scenarios are related to the amount of space at the top of the bottle in my opinion.

Now, oxidised beer could be an issue, so I'd leave them as they are but sup the beer relatively soon rather than storing them for months. I wouldn't mess about trying to re bottle them.
So how much space have you left? "quite a few inches" is a bit vague.
Also, what beer is it and how strong?
My thinking is that "quite a few inches" could take you well below the neck of the bottle and leave lots of air in there. I'm also thinking that I'd be inclined to top up with boiled and cooled water rather than pour the beer from one bottle to another.
Otherwise I agree with Cwrw, a centimetre is more than enough.
With PET bottles, I tend to add the priming sugar, fill the beer to within a couple of centimetres of the top and then squeeze the bottle until the liquid is right at the top before installing the cap. After a few hours in a warm place, the yeast will get to work generating carbon dioxide, the bottle will have expanded to its normal shape again and the couple of centimetres of space will have re-appeared at the top, but is this time entirely CO2.
1 teaspoon per 500ml is probably too much anyway but I would leave as they are. If you can get the whole batch into the fridge after they are carbonated that would be better.
I would just drink up the beer you've made and chalk it up to experience. I've made tons of gaffs along the way but it is rare that the beer can't be drunk and our beer making skills get better the more we brew. I've heard of people half filling bottles and the beer being fine. I wouldn't advise it, but the beer is going to be fine.
Thanks for all replies! Thanks @marshbrewer , yeah, I won't leave them too long.

@Cwrw666 - yup, 1cm - got it. For next time.

@An Ankoù - Sorry, yes, I was vague because it's embarrassing. It's about 3 inches from the top, coming under the start of the bottle neck. The kit was just a Bulldog Brews IPA, 5.5 ABV. Good to know about the water as an option, thank you.

@tigertim - Good to know about the squeezing, may try next time with the PET bottles.

@Guybrush Threepwood - ah yes, I have since read that bottling wands do this - I might look into getting one for next time.

@Caramel Ox - Good to know, I'll get them in the fridge when they're ready.

@Bitter_Dave - Thanks, good to know! I feel a bit more at ease now.
If you are using a bottling wand, you will find the wand displaces the perfect amount if the bottle is filled right to the top before removing (if that makes sense?)
I have found that I get reduced oxidation if I tilt the bottle after removing the wand and leave less headspace again by topping up. Leaving the wand valve push against the bottle neck. but yup leaving no more than 1 cm headspace as mentioned by @Cwrw666
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