There’s nothing worse than a flat beer, and this happened to me a few times before I realized what would go wrong. Homebrewing is sometimes tricky and you won’t make the best brew from the very first attempt, but once you master the fundamentals, it will never fail you again.
I remember brewing a stout that ended up acidic, then I fixed it after I realized the sanitization wasn’t on point, but then some of my beers went flat. I was confused about what could have gone wrong and checked every single possibility until I found that the mistake was in my lack of focus.
You see, I failed to measure the priming sugar properly because the spoon I used wasn’t of the measure I expected it to be. After I fixed this mistake my beer was never flat again, however in your case, there might be something else that’s causing you a flat beer, so let’s find out what is it.
Your beer may end up flat if you used the incorrect measure of priming sugar, the wrong sugar type, kept the bottles cold instead of at room temperature, if the yeast died in a meantime, or if you never gave the bottles time to carbonate naturally.
Let’s what’s there you can do to fix these mistakes for the next batch and is there hope to save your current, ruined one.
1. Dead yeast
Yeast may die when exposed to high temperatures which are way over the limit at which it can produce. Therefore, it’s important that you first try to remember did you ever expose your brew to high temperatures. Yeast usually dies at anything greater than 86°F (30°C ) but check the temperature tolerance for the type of yeast you used.
The second possibility is that you brewed a high ABV brew and the yeast can no longer work within an alcoholic environment that passes its tolerance.
If the latter is the case you’ll need to buy yeast with high ABV tolerance and if the temperature was the problem you better pitch new yeast.
2. Incorrect measurement of priming sugar
This may seem like an easy task, but homebrewers often make mistakes at this point. Measurements can be confusing for beginners especially when you have to convert from ounces to grams per liter and gallon and vice versa.
In my case, I accidentally came to the opinion that the measuring spoon I bought was calibrated at 5 grams exactly, but instead, it was meant for 1-pint bottles and counted 3.5 grams. Moreover, I prepared a priming solution and had to convert ml to the gram to see how much should I add to each bottle which additionally added to the confusion.
As a result, I added around 2.5 grams of sugar which were not enough to properly carbonate my bottles and I wasn’t aware of this at all.
3. You accidentally underprimed and overprimed bottles
If you bulk primed by adding priming solution into the entire batch prior to feeling bottles, there’s a chance that the sugar didn’t dissolve equally.
Bulk priming can be tricky and requires stirring. If this is done in the wrong way you may end up with some bottles underprimed and flat, while others may be overprimed or even cause bottle bombs.
4. The wrong sugar type
There are many options you have when it comes to priming sugar but what’s the point of complicating things when simple corn sugar will do the job efficiently and effectively.
Priming sugar is there only for carbonation purposes and it shouldn’t be used for flavoring.
Sugars have different fermentability potential, so the simpler, the better. If you used honey, it may be a problem because it’s impossible to say how much honey you need without knowing its gravity and every honey is different from another. So, it’s best to never use honey for priming purposes.
5. Storing bottles at the wrong temperature and not long enough
Homemade beer may need 2 weeks to properly carbonate even at room temperature, so if you stored them in a colder place like in a fridge it can take a few more weeks for carbonation to naturally occur in a cold place.
If you used some sugar that’s harder to ferment, you may need extra time like another week or two.
How to fix your flat bottles?
1. Put them in a warmer place
If you think you’ve put enough priming sugar in your beer and that yeast is still alive there’s nothing else but to let your bottles more time to naturally carbonate at a warmer temperature. Beer conditions faster just as the yeast converts sugars into alcohol and Co2 at warmer temperatures.
Make sure the temperature is between 64.4°F (18°C) and 71.6°F (22°C) to hit the golden spot at which most yeast will aggressively convert that sugar into Co2 in the shortest amount of time.
Let them sit for up to two weeks and then crack one and see did it help, in case it’s not carbonated you can give it more time, but I think it won’t help it and there’s a problem in something else. You see, letting your beer condition for an extra month will make it taste better, but there isn’t a point in expecting that beer will get more carbonated if it hasn’t already in 2-3 weeks at a warm temperature.
2. Reopen bottles and prime them again
This is the option you do when extra weeks at room temperature didn’t produce enough carbonation or when you know that you screwed with the wrong sugar, or measurement or the yeast died.
Open each bottle and put more sugar in and simply close the bottles and let them condition again, but be careful of the following things.
In case of incorrect measurements
If you know that you put only 2 grams instead of 4, simply add the missing 2 grams + at least 50% bonus grams to make up for the loss of Co2 which is in this case 1 bonus gram.
You see, if you have put some sugar at the beginning it means your beer is slightly carbonated, but once you pour it into a glass it may become flat because there’s not enough Co2 buildup.
In such a case, you should put bonus grams to make up for the loss of Co2 you’ll lose when you open a bottle. I must be honest and say that I have no clue how much existing Co2 will evaporate when you open the bottles, but I guess that if you add a full measurement of new sugar It won’t cause the bombs if you are still following some limits and not going with the absurd amount. (Although beer bottles are pretty pressure tolerant, place the bottles in a safe place to protect against bottle bombs, just in case).
The mentioned applies to situations when you know the yeast had enough time to make Co2 out of sugar and in such cases bottle bombs will rarely occur.
If it hasn’t been enough time, there might be still some sugar trapped in a bottle and no Co2 will evaporate, so when you add new sugar you could easily over carbonate your beer and cause bottle bombs, so always first make sure the yeast had enough time to eat the remaining sugar as I mentioned in a step above.
3. Mix new yeast with sugar
If you suspect the yeast is dead you should pour some yeast into each bottle with new priming sugar. The measurements here for the yeast are not super important because some extra yeast won’t hurt your beer nor cause bottle bombs. However, try to equally distribute no more than 0.18 oz (12 grams) of yeast per 5 gallons (23 liters) of beer because too much yeast can affect the taste.
If you don’t have that much yeast, probably even half as much will work but I have a strong policy when dealing with yeast, I like it strong and healthy which leads to powerful colonies.
Always let the homebrew enough time in the fridge prior to opening the bottle and drinking it. Sometimes the brew may be perfectly carbonated but serving it at warm temperatures will make the Co2 evaporate instantly.