How Do I Stop Exploding Beer Bottles?

exploding beer bottles

You have been exploring the world of homebrewing beer and enjoying the hobby. But a problem is disrupting your process and causing a safety hazard: your bottles explode during fermentation. Here’s why this happens and how you can stop exploding beer bottles.

Over-fermentation after bottling must be avoided to prevent homebrew beer bottles from exploding. Some ways to achieve such prevention are thoroughly sanitizing bottles, carefully measuring priming sugar, and only bottling the beer once it has fermented entirely.

A brief answer to this predicament leaves you with more questions than you started with. You know that uncontrolled fermentation is a problem. But how do you control fermentation to stop this issue before it begins? How much pressure can a bottle hold? We’ll examine bottle bombs and how to prevent them.

Why Does My Beer Keep Exploding?

Beer is made by fermenting wort. The yeast you add to the wort digests the glucose and produces ethyl alcohol (ethanol) and carbon dioxide as by-products. The carbon dioxide gas makes the beer carbonated, which is a quality we desire in beer.

However, if the fermentation process produces too much carbon dioxide, the pressure inside the bottle builds up until it can no longer contain it. At this point, the bottle’s structural integrity fails, exploding, spraying beer and shards of glass everywhere.

You may wonder why fermentation occasionally produces too much carbon dioxide but not at other times. After all, you have managed to brew beer without the bottles exploding. What is so different this time?

Why Do Beer Bottles Explode?

If you take the beer out of the fermenter too early, it will not have finished fermenting, i. e. it will be under-fermented. After you bottle it, it will carry on fermenting in the bottle because you have filled the bottles to the point that it would only be safe for a fully-fermented beer. The ongoing carbon dioxide production produces too much gas for the remaining volume inside the bottle.

Be careful if fermenting in a plastic bucket, as the cover may not seal well. You could interpret the lack of carbon dioxide bubbles from the airlock as a sign that fermentation is complete, not realizing that it is leaking from under the cover.

If you over-prime the beer after fermentation is complete, in other words, if you add more priming sugar than the recipe stipulates, you will also cause this problem. The yeast will revel in all the sugar, producing loads of carbon dioxide. Again, the volume of gas inside the bottle causes the pressure to build up to a point where the bottle fails.

If you use poor-quality bottles, such as reused twist-off bottles, they may fail even if the brew is not over-carbonated. Invest in quality bottles; you will be safer, and so will your beer.

If you store your beer in a warm place, especially one exposed to light, you will ruin your beer. Not only will it be light-struck, which results in skunking, but it will also ferment more, potentially resulting in a bottle bomb.

When you do not carefully sanitize reused bottles before bottling your beer you may pick up a wild yeast strain that behaves differently than the Saccharomyces cerevisiae strain you added. This strain may ferment drier, converting more sugar to alcohol and carbon dioxide than you intended.

This last problem can sometimes occur even if you are meticulous in your sanitary procedures. Some home brewers have brewed for years before experiencing a bottle bomb. Brettanomyces yeasts are particularly troublesome in this regard, as they ferment much drier than Saccharomyces strains.

How Much Pressure (PSI) Can A Beer Bottle Hold?

We are discussing situations where the volume of carbon dioxide inside your bottles results in more pressure than the bottle can handle. But different beer styles require different amounts of carbonation, ranging from stouts and porters with low carbonation, through most lagers and ales, to Belgian-style beers and hefeweizens with high carbonation.

So you may well ask how much pressure a beer bottle can take. Specifically, how many pounds per square inch (psi) they can hold. The answer is that it varies from bottle to bottle, and you should understand how manufacturers make bottles to select an appropriate bottle for your brew and avoid bottle bombs.

Many US manufacturers make bottles by a process known as press and blow, which results in a fairly thin bottle only intended for single use. Reusing such bottles is dangerous. Most European-made bottles are produced using the blow-and-blow method, which results in a thicker and heavier vessel that you can reuse many times.

Seek Out Blow And Blow Bottles For Home Brewing

Industry-standard wine and beer bottles (longnecks) are generally rated to around 3 atmospheres, equivalent to 45 psi. Grolsch warrants their bottles to 3.5 atmospheres or about 51 psi. Green Flash, a popular San Diego-based craft brewery, packages its beers in heavy glass bottles that are highly suitable for reuse.

Choose heavier bottles if you are brewing a heavily-carbonated style, such as a lambic, Belgian dubbel or tripel, or a hefeweizen. You can bottle in champagne bottles, which can hold as much as 6 atmospheres or 90 psi.

How Do You Prevent Bottle Bombs?

Not only are bottle bombs a waste of beer, but they are also extremely dangerous. When the bottle explodes, tiny shards of glass fly out at high velocity and could shred your hands and face or go into your eyes and destroy your sight.

To prevent this from happening, exercise caution when brewing. Ensure that you use only high-quality ingredients, such as good liquid yeast, and use it before it expires to avoid unexpected results. When reusing bottles, scrub and sanitize them thoroughly to prevent contamination with wild yeasts.

Measure out the priming sugar according to the recipe, and do not add more than required. Weigh it out rather than measuring by volume, as the weight of a cup of sugar varies enormously between suppliers of sugar.

Measure the specific gravity after you have chilled the wort and before you pitch the yeast; this is the original gravity (OG). Measure specific gravity again when fermentation is complete; this is the final gravity (FG). Ensure that you have the correct FG for the style of beer you are brewing. High-gravity beers will need to be fermented longer, so wait longer to take the beer out of the fermenter.

Use good-quality bottles for bottling your beer, preferably reusable bottles from a homebrew store. Stick with blow and blow bottles, and exercise caution if you doubt whether they are heavy-duty enough to handle the carbonation in a particular style of beer. Inspect them before use to identify any cracks or chips.

Ferment your beer in a cool, dark place to prevent over-fermentation

We advise you to sample your beer in the bottles before it is officially ready. If you get any gushers, discard them, as they are en route to being bottle bombs.

Pop the caps off all the other bottles in that batch to check whether they are over-carbonated, and reseal. Stick them into the fridge to slow fermentation, and drink as soon as possible.

When you sample the beer as we have described, ensure that you wear gloves, safety goggles, and thick clothing. You do not want to be caught by a bottle bomb at close range; the shards of flying glass could permanently disfigure or cripple you.


Exploding beer bottles represent a severe hazard. To prevent bottle bombs, we recommend you use sturdy bottles from your homebrew store, sterilize them to avoid wild yeast contamination, carefully weigh the priming sugar, and ensure that fermentation is complete before bottling the beer.

Dan Specht

Dan has been homebrewing beer for 8 years and holds a level 2 certifiication as a Cicerone.

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