Fail Of The Week: Exploding Fermentation

It’s no secret that hackers like fermentation, both the process and the end results. I myself have a crock of sauerkraut happily bubbling away in the kitchen right now. Fermentation can lead to tasty endpoints, and the process itself, which basically amounts to controlled rotting, is a fascinating set of biochemical reactions. But done wrong, fermentation can result in injury, as it did at CCC this year when a fermentation vessel exploded.

"It was the one on the left, officer. He did it."
“It was the one on the left, officer. He did it.”

Exactly what happened isn’t really clear, except that Food Hacking Base ran a number of workshops at CCC 2015, several of which involved fermented foods or drinks. A Grolsch-style bottle with a ceramic flip-top was apparently used as a fermentation vessel, but unfortunately the seal was not broken. The bottle found its way to another tent at CCC, this one running an SMD soldering workshop. Carbon dioxide gas built up enough pressure in the bottle to shatter it and send shrapnel flying through the workshop tent. According to a discussion thread on the incident, “people got hurt and need to go to the hospital because glas [sic] particles were stuck in their faces, a throat was cut and an eyelid bleeding.” The explosion was quite energetic, because, “we also found a 20cm long piece of glass that went trough [sic] the ceiling of the tent and propelled for another 4-5 meters afterwards.”

We’ve seen lots of Hackaday projects involving instrumentation and automation of fermentation, including some with really large vessels. The potential for destruction if such a vessel isn’t properly vented is pretty high. At the very least, you’ll be left with a really big mess to clean up. Be careful out there – microbes are not to be trifled with. We don’t want to give you the wrong idea about CCC; this year was incredible as [Elliot Williams] reported during his time there.

Now it’s off to the kitchen to check on my kraut.

[Thanks to Morgan for the tip.]

59 thoughts on “Fail Of The Week: Exploding Fermentation

      1. Everyone that makes beer properly finishes fermentation in a sealed bottle, that’s how you get it carbonated. Unless you cheat and use a CO2 tank and just shake the keg. I have 36 bottles in my basement right now that I intentionally added sugar to and capped off tight.

          1. Once I added a little to much sugar, and got a little to much CO2. One bottle in a case of 24 failed and took out most of the case with it. It happen at around 2am which woke me from a sound sleep on the 2nd floor of my house and the case was in the basement. Needles to say that there was glass and beer everywhere, with glass stuck in the ceiling and walls.

            I think my mistake happened because the primary fermentation was not complete when I bottled.

          2. Yeah, the first rule of homebrewing is patience…next to sanitize, sanitize, sanitize. Check your gravity; beginning and final. Your final gravity should be roughly 1/4 your original…always before you bottle. If it doesn’t reach that, then other measures need to be taken to get the ferment to finish.

        1. I force carb usually. But even if you are going the natural route you let fermentation finish, then you restart it with add sugars for bottling. The amount should be just enough to carbonate the drink, not enough to get the bottles pressurize anywhere near the failing point.

  1. Grolsch bottles can be quite thick… I’d imagine they’d have a lot of energy after they explode, and lots of sharp shrapnel…

    I’ve had a few bottles of home brewed beer in old red stripe bottles blow, and a few in regular beer bottles…

    After the first one goes the rest of the batch goes into the fridge to chill (stops the yeast from making more CO2, and lowers the pressure thanks to the ideal gas law) and a party is thrown to drink them before they can cause any more damage… need something a little more aggressive than the surgeon generals alcohol warning on the label though.

    1. I’ve had saison blow while bottle carbonating (at about 90F). I always keep them in a plastic bin for this reason until the carbonation is done. Interestingly it blows the bottoms off of regular beer bottles. When this happened I filled the plastic tub they were in with ice-water.

      Now drinking them was a trick. Popping the caps resulted in a champagne-like geyser. Ha!

      1. The only near explosive incident I had was some strawberry wine. I filled the container too full and some of the pulp pushed up and clogged the airlock. I noticed this at about 2AM, as I wandered into the kitchen for a glass of water. I thought, I better unclog that before it pops off. Upon removing the stopper, a fountain of strawberry pulp shot from the container. Cleaning strawberry off of your ceiling is not what I was expecting to do in the middle of the night.

    2. I once left a specific gravity meter floating in a demijohn to keep monitoring it continuously, but it floated towards the bubble lock tube and got sucked in by the stream of gas exiting the bottle. Unfortunately this one had a screw-on top so the cork didn’t blow and instead the pressure shot the bubble lock clean off and the gravity meter bulb shattered as it went through the hole.

      The stem of the meter lodged itself in the ceiling.

    1. Oh, c’mon. Don’t get your pants in a twist. A few got hurt, but it’s only a scratch, nothing a few stitches couldn’t fix. Lick your wounds, have another beer. Cheers!

  2. TFA indicates that they were not supposed to have sealed the bottle. It seems like in this situation the correct course of action is to set your students up without the swingtop attached, and hand out sanitized squares of foil to place over the top. Foil wrapped over the top of a glass vessel is a time honored “good enough” measure presuming quite active fermentation (or lack of airlocks). Don’t get me wrong, I am all about personal responsibility, but whoever was running this fermentation workshop knew they weren’t dealing with master brewers and had the ability to prevent any accidental bombs.

  3. Just yesterday I was looking at one of these glass bottles (mine from World Market) and wondering how well they’d fare for carbonating. I guess they do quite well, but have their limits.

    1. Not any bottle of that model can be reliable for carbonating… several brands are for decorating your kitchen and may not be designed to withstand stresses of the pressure built AND stress of the lever anchor points at the top of the bottle…

    2. The clear flip top bottles sold in supermarkets, sometimes in the furniture/decoration isle, are made of cheap window glass and can’t really take heat or pressure. Simply washing them in hot water can cause cracks.

      If you want to use glass bottles, use ones that have a return fee, because they’re made of stronger borosilicate glass to withstand steam washing and transportation. When they shatter, they don’t make such sharp pointy shards as simple low quality soda-lime glass, but instead tend to just pop the bottom off.

      1. PIcture caption: “It was the one on the left, officer. He did it.”

        Those bottles in the picture are exactly the kind that can’t take any sort of pressure. It’s the square shape combined with the cheap glass. These are purely for decoration.

  4. That’s definitely a great field of experimentation…
    I build myself some alambics when enough time build up and they can be quite dangerous too when operated, luckily the fermentation before distillery itself is with a bubbler so no pression builds up.
    It is obvious that my usage of an alambic is for small scale essential oil production from the garden plants I grow, and that producing distilled alcohol spirits is prohibited in most countries… tolerated for home scale in some.
    My first one was a converted pressure cooker with pneumatic quick connectors to fit all elements and then put it back in the dishwasher, but the second in planning is a 30L copper islay type pear alambic for achieving the same beverage as our scottish pals :-)

  5. Guess you young ‘uns don’t remember the days of exploding pressure cookers, before all this modern safety stuff. Not generally fermentation related, true, but the mess can be similar. I once redecorated my entire kitchen with bean soup.

      1. One use is when you need to cook a food above the boiling point, particularly if you live in high elevations where the boiling point is low. Also, pressure canning is needed when canning low acid foods, fish, and meats, where the boiling point is not hot enough to destroy bacterial spores that can cause spoilage.

      2. We still use pressure cookers, it’s just that now they have better & redundant safety valves that so they no longer explode. As Nick mentioned below, they cut cooking time way down, and are especially useful for things like dried beans that otherwise need a long soak or a long cooking time or both.

        As I write this, I’m using my modern, boring pressure cooker to make bean soup. Not only will it be yummy, it will also allow me to, getting back to the original topic, do some fermentation experiments (if you know what I mean).

  6. Simple solution avoiding glass shrapnel: use plastic fizzy drink bottles. They distend quite beautifully under internal pressure, so you can judge when they are “ready”. Also they won’t shatter in the same way as glass.

    1. Well… sorta. I’m not saying how I know, but if you half-fill a 2-liter ginger ale bottle with warm water and add about half a pound of dry ice, twist the cap on it and toss it in the backyard… Well, let’s just say it’s not a good thing to do when you have neighbors.

    2. My sister and mother are in to that craze where they ferment juices with kefir granules. The problem was when they carbonated them in grolsch bottles. According to them, it was safe because they “burped” them every day. Sure enough, one detonated near me: luckily it was behind something so the only injuries were ringing ears. It had been “burped” 3 hours before. That finally convinced them that maybe I had a point about hour dangerous it was.

      I bought some 0-20 psi relief valves and 2 liter pop bottles. Screwed the valves into the caps and set them to 12 psi. Carbonation without the boom.

        1. It’s not a great idea because when the pressure relief valve opens and the drinks starts to bubble, it can foam up into the valve and block it.

          It only works if there’s sufficient headroom in the vessel for the bubbles to break, which for a 2 liter bottle might mean leaving it half empty.

          1. They’re 1/4″ ball+ spring valves: “foam” isn’t going to plug them. Also, kefir fermentation isn’t that energetic. They’ve fermented everything under the sun, and not once has there been more than an inch of foam.

            Secondly, the valves are hot glued in. I can easily pull them off with my hands. That weak joint is going to fail long before the bottle does.

        2. Think I bought them from Grainger online. They’re the ball bearing and spring type, 1/4″. Make sure you check that they’re set to relieve pressure: mine arrived set up for vacuum. I also attached then with a softer hot melt glue to serve as a secondary safety for the unlikely event the valve fails.

  7. ALWAYS — ALWAYS — ALWAYS use a pressure release valve when fermenting. No exceptions. If you want to carbonate “in the bottle” you /must/ do so under the most controlled conditions ( it’s called ‘conditioning’ for a reason ) and then cool the bottle to near-freezing temperatures to stop the fermentation, then leave it cold until it’s opened.

    Fermenting under pressured conditions in a sealed glass or plastic bottle is -always- tempting fate. Know your chemistry, know your biology, and for Pete’s sake .. always keep glass containers well contained in a box or with plastic mesh to prevent injury should they decide to suffer a catastrophic failure.

    1. If you run your batch dry, there’s no danger of bottle explosion because it just doesn’t ferment any further. Mixing the carbonating sugar in the whole batch instead of spooning it into the bottles then ensures that you get an even distribution and no surprise bottles.

      It’s just the greedy brewer who puts too much fermentables in to get high ABV, and the hasty brewer who bottles too early.

  8. This is nothing new.

    The reason bubbling wine (Champagne and the like) was once so rare and expensive is that the secondary fermentation (that produced carbonation) would destroy most of the bottles. This was considered a detriment at the time since it ruined most of the vinyards’ profits as well. Dom Perignon himself spent a lot of time trying to get rid of the bubbles that were eventually the chief source of profit for the appellation once the Brits (and the world) decided that they liked it better with bubbles.

    Exploding bottles are a known hazard among home brewers/winemakers and we’ve all had bottles go at one point or another. Keeping them separated by dividers in cases to prevent chain-explosions, and wrapped in a towel if you’re not sure while handling mitigates the hazard.

    If it matters, I have a relative who lost a year’s production of wine that had fermented in the bottle and all went up at once when he slammed the door to the storage cellar. Fortunately he was leaving.

    1. Actually, Dom Pergnon’s problem was that it was damn hard to get the yeast to settle down in bubbly wine. It made the wine cloudy.

      You had to leave the bottles open to get rid of the bubbles, then settle the yeast and decant the bottle, but that would oxidize the wine and it wouldn’t keep, turning into vinegar instead.

      The problem was solved when they figured out a way to freeze the neck of the champagne bottle in brine, so they could leave the bottles neck-down in the rack and collect all the detritus against the cork. Then they’d make a freeze plug and blow the yeast out from the bottle, and re-cork it.

  9. I love to ferment just as much as the rest of you. After some blow ups I now do two things for safer storage.

    1) Make or buy a temp controller to convert you chest freezer into a the ideal summer beer storage space. You can store your beers at 72F for fermentation and drop it down to 55F for long term storage.

    2) Consider using a growler or CO2 setup. I didn’t want to get into a whole keg size as I am traveling a lot, but a little insulated growler that takes CO2 cartridges is ideal and there are a few to choose from now. If you saison, mead or kombucha is feeling a little flat just charge it up.

  10. And all this can be avoided with some math and know-how. First of all: USE AIRLOCKS FOR FERMENTATION! And inspect them twice a day at least. If you don’t have airlocks, use ball of cotton wool as stopper. Secondly, if you want to make it carbonated, you calculate sugar content before fermentation, and later after it ended to know, how much sugar you need to add before bottling. You add too little, and there won’t be bubbles at all. Too much and you end up with exploding bottles. Brewers all over the world know this. I made my own wine and beer for past six years, so I have some experience. I never had any explosions.

  11. Never once had a blow up, use a blow off tube for really big beers, and use the correct amount of priming sugar/honey once the initial fermentation has finished.

    If your bottles are blowing up, you did something wrong either too much priming sugar/honey or you have a contamination of bacteria. The most obvious symptom being a geyser upon opening. You may think bacteria smackteria but these little guys produce methanol, and horrible flavors from aldehydes. Try brewing in glass and really scrubbing, not scouring to remove dust and debris.

    If you are purposefully brewing with bacteria, you aren’t reading this because it is elementary. If you do it right it is delicious, using lactobacillis New Belgiums Mothership Wit is the bomb!

  12. For some reason, it always seems surprising to me that the yeast can create so much pressure in the bottle that it explodes. Naively, I feel like there should be some physical or chemical reason preventing the yeast from continuously pumping out carbon dioxide indefinitely. The alcohol content of a fermented drink is self-regulating because eventually the yeast creates so much ethanol that it can no longer survive. Surely there’s some equivalent point where the pressure kills the organism, or at least disrupts its processes enough that it stops?

  13. Pressure fermentation in glass is dangerous, and the explosions can be very energetic.

    Fermenting in PET plastic is safer because:
    1) No flying glass
    2) It’s easy to test the pressure : Can’t dent the bottle with your thumb? Into the fridge.

    You still need to monitor your brew though, while exploding PET is safer than glass, it’s still dangerous, not to mention messy.

    1. Long term fermentation in PET bottles has its downsides. The PET allows for oxygen to wander through the plastic and oxidize the beer. The plastic beer bottles you sometimes see, are special with I believe a thin layer of metal sandwiched between PET layers.

  14. They is another anecdote related to the event happend on this years chaos communication camp: after it happend, they called the C.E.R.T, Chaos Emergency Response Team, which is the central hub for emergency, medical and technical issues. On the phone, the C.E.R.T dispatcher misunderstood “a glas bottle exploded” to “a gas bottle exploded” which lead to the stationed fire truck rushing over the camp with its siren blaring.

  15. The belgian brewery i visited this spring, they make geuze with fermentation in closed bottles, use glass bottles made in Germany. No coincidence I think, you need to get the right stuff.

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